Hello,
syzbot found the following crash on:
HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10bfe282e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com
================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [inline] BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 Read of size 16 at addr ffff888094b0aa10 by task syz-executor414/9999
CPU: 0 PID: 9999 Comm: syz-executor414 Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:638 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 memcpy+0x24/0x50 mm/kasan/common.c:124 memcpy include/linux/string.h:380 [inline] fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 con_font_get drivers/tty/vt/vt.c:4446 [inline] con_font_op+0x20b/0x1250 drivers/tty/vt/vt.c:4605 vt_ioctl+0x181a/0x26d0 drivers/tty/vt/vt_ioctl.c:965 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4444d9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fff6f4393b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fff6f4393c0 RCX: 00000000004444d9 RDX: 0000000020000440 RSI: 0000000000004b72 RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000400da0 R10: 00007fff6f438f00 R11: 0000000000000246 R12: 00000000004021e0 R13: 0000000000402270 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 9999: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] __kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:485 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:526 __do_kmalloc mm/slab.c:3656 [inline] __kmalloc+0x163/0x770 mm/slab.c:3665 kmalloc include/linux/slab.h:561 [inline] fbcon_set_font+0x32d/0x860 drivers/video/fbdev/core/fbcon.c:2663 con_font_set drivers/tty/vt/vt.c:4538 [inline] con_font_op+0xe18/0x1250 drivers/tty/vt/vt.c:4603 vt_ioctl+0xd2e/0x26d0 drivers/tty/vt/vt_ioctl.c:913 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 9771: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] kasan_set_free_info mm/kasan/common.c:334 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:473 kasan_slab_free+0xe/0x10 mm/kasan/common.c:482 __cache_free mm/slab.c:3426 [inline] kfree+0x10a/0x2c0 mm/slab.c:3757 tomoyo_init_log+0x15c1/0x2070 security/tomoyo/audit.c:294 tomoyo_supervisor+0x33f/0xef0 security/tomoyo/common.c:2095 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline] tomoyo_env_perm+0x18e/0x210 security/tomoyo/environ.c:63 tomoyo_environ security/tomoyo/domain.c:670 [inline] tomoyo_find_next_domain+0x1354/0x1f6c security/tomoyo/domain.c:876 tomoyo_bprm_check_security security/tomoyo/tomoyo.c:107 [inline] tomoyo_bprm_check_security+0x124/0x1a0 security/tomoyo/tomoyo.c:97 security_bprm_check+0x63/0xb0 security/security.c:784 search_binary_handler+0x71/0x570 fs/exec.c:1645 exec_binprm fs/exec.c:1701 [inline] __do_execve_file.isra.0+0x1329/0x22b0 fs/exec.c:1821 do_execveat_common fs/exec.c:1867 [inline] do_execve fs/exec.c:1884 [inline] __do_sys_execve fs/exec.c:1960 [inline] __se_sys_execve fs/exec.c:1955 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1955 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff888094b0a000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 2576 bytes inside of 4096-byte region [ffff888094b0a000, ffff888094b0b000) The buggy address belongs to the page: page:ffffea000252c280 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0 raw: 00fffe0000010200 ffffea0002a3ae08 ffffea0002a6aa88 ffff8880aa402000 raw: 0000000000000000 ffff888094b0a000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff888094b0a900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888094b0a980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888094b0aa00: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^ ffff888094b0aa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888094b0ab00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================
--- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
On Tue, Dec 3, 2019 at 11:25 PM syzbot syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com wrote:
Hello,
syzbot found the following crash on:
HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10bfe282e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com
================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [inline] BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 Read of size 16 at addr ffff888094b0aa10 by task syz-executor414/9999
So fbcon allocates some memory, security/tomoyo goes around and frees it, fbcon goes boom because the memory is gone. I'm kinda leaning towards "not an fbcon bug". Adding relevant security folks and mailing lists.
But from a very quick look in tomoyo it loosk more like "machine on fire, random corruption all over". No idea what's going on here. -Daniel
CPU: 0 PID: 9999 Comm: syz-executor414 Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:638 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 memcpy+0x24/0x50 mm/kasan/common.c:124 memcpy include/linux/string.h:380 [inline] fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 con_font_get drivers/tty/vt/vt.c:4446 [inline] con_font_op+0x20b/0x1250 drivers/tty/vt/vt.c:4605 vt_ioctl+0x181a/0x26d0 drivers/tty/vt/vt_ioctl.c:965 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4444d9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fff6f4393b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fff6f4393c0 RCX: 00000000004444d9 RDX: 0000000020000440 RSI: 0000000000004b72 RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000400da0 R10: 00007fff6f438f00 R11: 0000000000000246 R12: 00000000004021e0 R13: 0000000000402270 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 9999: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] __kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:485 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:526 __do_kmalloc mm/slab.c:3656 [inline] __kmalloc+0x163/0x770 mm/slab.c:3665 kmalloc include/linux/slab.h:561 [inline] fbcon_set_font+0x32d/0x860 drivers/video/fbdev/core/fbcon.c:2663 con_font_set drivers/tty/vt/vt.c:4538 [inline] con_font_op+0xe18/0x1250 drivers/tty/vt/vt.c:4603 vt_ioctl+0xd2e/0x26d0 drivers/tty/vt/vt_ioctl.c:913 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 9771: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] kasan_set_free_info mm/kasan/common.c:334 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:473 kasan_slab_free+0xe/0x10 mm/kasan/common.c:482 __cache_free mm/slab.c:3426 [inline] kfree+0x10a/0x2c0 mm/slab.c:3757 tomoyo_init_log+0x15c1/0x2070 security/tomoyo/audit.c:294 tomoyo_supervisor+0x33f/0xef0 security/tomoyo/common.c:2095 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline] tomoyo_env_perm+0x18e/0x210 security/tomoyo/environ.c:63 tomoyo_environ security/tomoyo/domain.c:670 [inline] tomoyo_find_next_domain+0x1354/0x1f6c security/tomoyo/domain.c:876 tomoyo_bprm_check_security security/tomoyo/tomoyo.c:107 [inline] tomoyo_bprm_check_security+0x124/0x1a0 security/tomoyo/tomoyo.c:97 security_bprm_check+0x63/0xb0 security/security.c:784 search_binary_handler+0x71/0x570 fs/exec.c:1645 exec_binprm fs/exec.c:1701 [inline] __do_execve_file.isra.0+0x1329/0x22b0 fs/exec.c:1821 do_execveat_common fs/exec.c:1867 [inline] do_execve fs/exec.c:1884 [inline] __do_sys_execve fs/exec.c:1960 [inline] __se_sys_execve fs/exec.c:1955 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1955 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff888094b0a000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 2576 bytes inside of 4096-byte region [ffff888094b0a000, ffff888094b0b000) The buggy address belongs to the page: page:ffffea000252c280 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0 raw: 00fffe0000010200 ffffea0002a3ae08 ffffea0002a6aa88 ffff8880aa402000 raw: 0000000000000000 ffff888094b0a000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff888094b0a900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888094b0a980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888094b0aa00: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^ffff888094b0aa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888094b0ab00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================
This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
On Tue, Dec 3, 2019 at 11:37 PM Daniel Vetter daniel.vetter@ffwll.ch wrote:
On Tue, Dec 3, 2019 at 11:25 PM syzbot syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com wrote:
Hello,
syzbot found the following crash on:
HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10bfe282e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com
================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [inline] BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 Read of size 16 at addr ffff888094b0aa10 by task syz-executor414/9999
So fbcon allocates some memory, security/tomoyo goes around and frees it, fbcon goes boom because the memory is gone. I'm kinda leaning towards "not an fbcon bug". Adding relevant security folks and mailing lists.
But from a very quick look in tomoyo it loosk more like "machine on fire, random corruption all over". No idea what's going on here.
Hi Daniel,
This is an out-of-bounds access, not use-after-free. I don't know why we print the free stack at all (maybe +Andrey knows), but that's what KASAN did from day one. I filed https://bugzilla.kernel.org/show_bug.cgi?id=198425 which I think is a good idea, I will add your confusion as a data point :) Re this bug, free stack is irrelevant, I guess it's when the heap block was freed before it was reallocated by console. So it's plain out-of-bounds in fbcon_get_font, which looks sane and consistent to me and reproducible on top.
CPU: 0 PID: 9999 Comm: syz-executor414 Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:638 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 memcpy+0x24/0x50 mm/kasan/common.c:124 memcpy include/linux/string.h:380 [inline] fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 con_font_get drivers/tty/vt/vt.c:4446 [inline] con_font_op+0x20b/0x1250 drivers/tty/vt/vt.c:4605 vt_ioctl+0x181a/0x26d0 drivers/tty/vt/vt_ioctl.c:965 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4444d9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fff6f4393b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fff6f4393c0 RCX: 00000000004444d9 RDX: 0000000020000440 RSI: 0000000000004b72 RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000400da0 R10: 00007fff6f438f00 R11: 0000000000000246 R12: 00000000004021e0 R13: 0000000000402270 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 9999: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] __kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:485 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:526 __do_kmalloc mm/slab.c:3656 [inline] __kmalloc+0x163/0x770 mm/slab.c:3665 kmalloc include/linux/slab.h:561 [inline] fbcon_set_font+0x32d/0x860 drivers/video/fbdev/core/fbcon.c:2663 con_font_set drivers/tty/vt/vt.c:4538 [inline] con_font_op+0xe18/0x1250 drivers/tty/vt/vt.c:4603 vt_ioctl+0xd2e/0x26d0 drivers/tty/vt/vt_ioctl.c:913 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 9771: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] kasan_set_free_info mm/kasan/common.c:334 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:473 kasan_slab_free+0xe/0x10 mm/kasan/common.c:482 __cache_free mm/slab.c:3426 [inline] kfree+0x10a/0x2c0 mm/slab.c:3757 tomoyo_init_log+0x15c1/0x2070 security/tomoyo/audit.c:294 tomoyo_supervisor+0x33f/0xef0 security/tomoyo/common.c:2095 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline] tomoyo_env_perm+0x18e/0x210 security/tomoyo/environ.c:63 tomoyo_environ security/tomoyo/domain.c:670 [inline] tomoyo_find_next_domain+0x1354/0x1f6c security/tomoyo/domain.c:876 tomoyo_bprm_check_security security/tomoyo/tomoyo.c:107 [inline] tomoyo_bprm_check_security+0x124/0x1a0 security/tomoyo/tomoyo.c:97 security_bprm_check+0x63/0xb0 security/security.c:784 search_binary_handler+0x71/0x570 fs/exec.c:1645 exec_binprm fs/exec.c:1701 [inline] __do_execve_file.isra.0+0x1329/0x22b0 fs/exec.c:1821 do_execveat_common fs/exec.c:1867 [inline] do_execve fs/exec.c:1884 [inline] __do_sys_execve fs/exec.c:1960 [inline] __se_sys_execve fs/exec.c:1955 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1955 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff888094b0a000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 2576 bytes inside of 4096-byte region [ffff888094b0a000, ffff888094b0b000) The buggy address belongs to the page: page:ffffea000252c280 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0 raw: 00fffe0000010200 ffffea0002a3ae08 ffffea0002a6aa88 ffff8880aa402000 raw: 0000000000000000 ffff888094b0a000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff888094b0a900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888094b0a980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888094b0aa00: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^ffff888094b0aa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888094b0ab00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================
This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
On Wed, Dec 4, 2019 at 7:33 AM Dmitry Vyukov dvyukov@google.com wrote:
On Tue, Dec 3, 2019 at 11:37 PM Daniel Vetter daniel.vetter@ffwll.ch wrote:
On Tue, Dec 3, 2019 at 11:25 PM syzbot syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com wrote:
Hello,
syzbot found the following crash on:
HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10bfe282e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com
================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [inline] BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 Read of size 16 at addr ffff888094b0aa10 by task syz-executor414/9999
So fbcon allocates some memory, security/tomoyo goes around and frees it, fbcon goes boom because the memory is gone. I'm kinda leaning towards "not an fbcon bug". Adding relevant security folks and mailing lists.
But from a very quick look in tomoyo it loosk more like "machine on fire, random corruption all over". No idea what's going on here.
Hi Daniel,
This is an out-of-bounds access, not use-after-free. I don't know why we print the free stack at all (maybe +Andrey knows), but that's what KASAN did from day one. I filed https://bugzilla.kernel.org/show_bug.cgi?id=198425 which I think is a good idea, I will add your confusion as a data point :) Re this bug, free stack is irrelevant, I guess it's when the heap block was freed before it was reallocated by console. So it's plain out-of-bounds in fbcon_get_font, which looks sane and consistent to me and reproducible on top.
Ugh, that's indeed very confusing, thanks for explaining. -Daniel
CPU: 0 PID: 9999 Comm: syz-executor414 Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:638 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 memcpy+0x24/0x50 mm/kasan/common.c:124 memcpy include/linux/string.h:380 [inline] fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 con_font_get drivers/tty/vt/vt.c:4446 [inline] con_font_op+0x20b/0x1250 drivers/tty/vt/vt.c:4605 vt_ioctl+0x181a/0x26d0 drivers/tty/vt/vt_ioctl.c:965 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4444d9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fff6f4393b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fff6f4393c0 RCX: 00000000004444d9 RDX: 0000000020000440 RSI: 0000000000004b72 RDI: 0000000000000005 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000400da0 R10: 00007fff6f438f00 R11: 0000000000000246 R12: 00000000004021e0 R13: 0000000000402270 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 9999: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] __kasan_kmalloc mm/kasan/common.c:512 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:485 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:526 __do_kmalloc mm/slab.c:3656 [inline] __kmalloc+0x163/0x770 mm/slab.c:3665 kmalloc include/linux/slab.h:561 [inline] fbcon_set_font+0x32d/0x860 drivers/video/fbdev/core/fbcon.c:2663 con_font_set drivers/tty/vt/vt.c:4538 [inline] con_font_op+0xe18/0x1250 drivers/tty/vt/vt.c:4603 vt_ioctl+0xd2e/0x26d0 drivers/tty/vt/vt_ioctl.c:913 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2658 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 9771: save_stack+0x23/0x90 mm/kasan/common.c:71 set_track mm/kasan/common.c:79 [inline] kasan_set_free_info mm/kasan/common.c:334 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:473 kasan_slab_free+0xe/0x10 mm/kasan/common.c:482 __cache_free mm/slab.c:3426 [inline] kfree+0x10a/0x2c0 mm/slab.c:3757 tomoyo_init_log+0x15c1/0x2070 security/tomoyo/audit.c:294 tomoyo_supervisor+0x33f/0xef0 security/tomoyo/common.c:2095 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline] tomoyo_env_perm+0x18e/0x210 security/tomoyo/environ.c:63 tomoyo_environ security/tomoyo/domain.c:670 [inline] tomoyo_find_next_domain+0x1354/0x1f6c security/tomoyo/domain.c:876 tomoyo_bprm_check_security security/tomoyo/tomoyo.c:107 [inline] tomoyo_bprm_check_security+0x124/0x1a0 security/tomoyo/tomoyo.c:97 security_bprm_check+0x63/0xb0 security/security.c:784 search_binary_handler+0x71/0x570 fs/exec.c:1645 exec_binprm fs/exec.c:1701 [inline] __do_execve_file.isra.0+0x1329/0x22b0 fs/exec.c:1821 do_execveat_common fs/exec.c:1867 [inline] do_execve fs/exec.c:1884 [inline] __do_sys_execve fs/exec.c:1960 [inline] __se_sys_execve fs/exec.c:1955 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1955 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff888094b0a000 which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 2576 bytes inside of 4096-byte region [ffff888094b0a000, ffff888094b0b000) The buggy address belongs to the page: page:ffffea000252c280 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0 raw: 00fffe0000010200 ffffea0002a3ae08 ffffea0002a6aa88 ffff8880aa402000 raw: 0000000000000000 ffff888094b0a000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff888094b0a900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888094b0a980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888094b0aa00: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^ffff888094b0aa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888094b0ab00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================
This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches
On 12/4/19 9:33 AM, Dmitry Vyukov wrote:
On Tue, Dec 3, 2019 at 11:37 PM Daniel Vetter daniel.vetter@ffwll.ch wrote:
On Tue, Dec 3, 2019 at 11:25 PM syzbot syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com wrote:
Hello,
syzbot found the following crash on:
HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10bfe282e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com
================================================================== BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [inline] BUG: KASAN: slab-out-of-bounds in fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 Read of size 16 at addr ffff888094b0aa10 by task syz-executor414/9999
So fbcon allocates some memory, security/tomoyo goes around and frees it, fbcon goes boom because the memory is gone. I'm kinda leaning towards "not an fbcon bug". Adding relevant security folks and mailing lists.
But from a very quick look in tomoyo it loosk more like "machine on fire, random corruption all over". No idea what's going on here.
Hi Daniel,
This is an out-of-bounds access, not use-after-free. I don't know why we print the free stack at all (maybe +Andrey knows), but that's what KASAN did from day one. I filed https://bugzilla.kernel.org/show_bug.cgi?id=198425 which I think is a good idea, I will add your confusion as a data point :)
Because we have that information (free stack) and it usually better to provide all the information we have rather than hide it. You never known what information might be needed to fix the bug. Free memory might be reused and what we report as OOB might be an UAF and free stack could be useful in such case.
syzbot has bisected this bug to:
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 Author: Russell Currey ruscur@russell.cc Date: Mon Feb 8 04:08:20 2016 +0000
powerpc/powernv: Remove support for p5ioc2
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
Hello.
syzbot is reporting that memory allocation size at fbcon_set_font() is too small because font's height is rounded up from 10 to 16 after memory allocation.
---------- diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index c9235a2f42f8..68fe66e435d3 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2461,6 +2461,7 @@ static int fbcon_get_font(struct vc_data *vc, struct console_font *font)
if (font->width <= 8) { j = vc->vc_font.height; + printk("ksize(fontdata)=%lu font->charcount=%d vc->vc_font.height=%d font->width=%u\n", ksize(fontdata), font->charcount, j, font->width); for (i = 0; i < font->charcount; i++) { memcpy(data, fontdata, j); memset(data + j, 0, 32 - j); @@ -2661,6 +2662,8 @@ static int fbcon_set_font(struct vc_data *vc, struct console_font *font, size = h * pitch * charcount;
new_data = kmalloc(FONT_EXTRA_WORDS * sizeof(int) + size, GFP_USER); + if (new_data) + printk("ksize(new_data)=%lu h=%u pitch=%u charcount=%u font->width=%u\n", ksize(new_data), h, pitch, charcount, font->width);
if (!new_data) return -ENOMEM; ----------
Normal usage:
[ 27.305293] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.328527] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.362551] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.385084] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.387653] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.417562] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.437808] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.440738] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.461157] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.495346] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.607372] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.655674] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.675310] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8 [ 27.702193] ksize(new_data)=8192 h=16 pitch=1 charcount=256 font->width=8
syzbot's testcase:
[ 115.784893] ksize(new_data)=4096 h=10 pitch=1 charcount=256 font->width=8 [ 115.790269] ksize(fontdata)=4096 font->charcount=256 vc->vc_font.height=16 font->width=8
On 04/12/19 22:41, syzbot wrote:
syzbot has bisected this bug to:
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 Author: Russell Currey ruscur@russell.cc Date: Mon Feb 8 04:08:20 2016 +0000
powerpc/powernv: Remove support for p5ioc2
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
Why is everybody being CC'd, even if the bug has nothing to do with the person's subsystem?
Thanks,
Paolo
On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini pbonzini@redhat.com wrote:
On 04/12/19 22:41, syzbot wrote:
syzbot has bisected this bug to:
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 Author: Russell Currey ruscur@russell.cc Date: Mon Feb 8 04:08:20 2016 +0000
powerpc/powernv: Remove support for p5ioc2bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
Why is everybody being CC'd, even if the bug has nothing to do with the person's subsystem?
The To list should be intersection of 2 groups of emails: result of get_maintainers.pl on the file identified as culprit in the crash message + emails extracted from the bisected to commit.
On 05/12/19 11:16, Dmitry Vyukov wrote:
On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini pbonzini@redhat.com wrote:
On 04/12/19 22:41, syzbot wrote:
syzbot has bisected this bug to:
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 Author: Russell Currey ruscur@russell.cc Date: Mon Feb 8 04:08:20 2016 +0000
powerpc/powernv: Remove support for p5ioc2bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
Why is everybody being CC'd, even if the bug has nothing to do with the person's subsystem?
The To list should be intersection of 2 groups of emails: result of get_maintainers.pl on the file identified as culprit in the crash message + emails extracted from the bisected to commit.
Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of backtrace and I get to share syzkaller's joy every time. :)
This bisect result is bogus, though Tetsuo found the bug anyway. Perhaps you can exclude commits that only touch architectures other than x86?
Paolo
On Thu, Dec 5, 2019 at 11:22 AM Paolo Bonzini pbonzini@redhat.com wrote:
On 05/12/19 11:16, Dmitry Vyukov wrote:
On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini pbonzini@redhat.com wrote:
On 04/12/19 22:41, syzbot wrote:
syzbot has bisected this bug to:
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 Author: Russell Currey ruscur@russell.cc Date: Mon Feb 8 04:08:20 2016 +0000
powerpc/powernv: Remove support for p5ioc2bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
Why is everybody being CC'd, even if the bug has nothing to do with the person's subsystem?
The To list should be intersection of 2 groups of emails: result of get_maintainers.pl on the file identified as culprit in the crash message + emails extracted from the bisected to commit.
Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of backtrace and I get to share syzkaller's joy every time. :)
I don't see any mention of "kvm" in the crash report. And it's only 1 file, not all of them, in this case I would expect it to be drivers/video/fbdev/core/fbcon.c. So it should be something different.
This bisect result is bogus, though Tetsuo found the bug anyway. Perhaps you can exclude commits that only touch architectures other than x86?
We do this. It work sometimes. But sometimes it hits non-deterministic kernel build bugs: https://github.com/google/syzkaller/issues/1271#issuecomment-559093018 And in this case it hit some git bisect weirdness which I can't explain yet: https://github.com/google/syzkaller/issues/1527
On 05/12/19 11:31, Dmitry Vyukov wrote:
Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of backtrace and I get to share syzkaller's joy every time. :)
I don't see any mention of "kvm" in the crash report.
It's there in the stack trace, not sure if this is what triggered my Cc:
[<ffffffff810c7c3a>] kvm_wait+0xca/0xe0 arch/x86/kernel/kvm.c:612
Paolo
On Thu, Dec 5, 2019 at 11:53 AM Paolo Bonzini pbonzini@redhat.com wrote:
On 05/12/19 11:31, Dmitry Vyukov wrote:
Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of backtrace and I get to share syzkaller's joy every time. :)
I don't see any mention of "kvm" in the crash report.
It's there in the stack trace, not sure if this is what triggered my Cc:
[<ffffffff810c7c3a>] kvm_wait+0xca/0xe0 arch/x86/kernel/kvm.c:612
Paolo
Oh, you mean the final bisection crash. Indeed it contains a kvm frame and it turns out to be a bug in syzkaller code that indeed misattributed it to kvm instead of netfilter. Should be fixed now, you may read the commit message for details: https://github.com/google/syzkaller/commit/4fb74474cf0af2126be3a8989d770c394...
Overall this "making sense out of kernel output" task is the ultimate insanity, you may skim through this file to get a taste of amount of hardcoding and special corner cases that need to be handled: https://github.com/google/syzkaller/blob/master/pkg/report/linux.go And this is never done, such "exception from exception corner case" things pop up every week. There is always something to shuffle and tune. It only keeps functioning due to 500+ test cases for all possible insane kernel outputs: https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/re... https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/gu...
So thanks for persisting and questioning! We are getting better with each new test.
On 05/12/19 12:27, Dmitry Vyukov wrote:
Oh, you mean the final bisection crash. Indeed it contains a kvm frame and it turns out to be a bug in syzkaller code that indeed misattributed it to kvm instead of netfilter. Should be fixed now, you may read the commit message for details: https://github.com/google/syzkaller/commit/4fb74474cf0af2126be3a8989d770c394...
Overall this "making sense out of kernel output" task is the ultimate insanity, you may skim through this file to get a taste of amount of hardcoding and special corner cases that need to be handled: https://github.com/google/syzkaller/blob/master/pkg/report/linux.go And this is never done, such "exception from exception corner case" things pop up every week. There is always something to shuffle and tune. It only keeps functioning due to 500+ test cases for all possible insane kernel outputs: https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/re... https://github.com/google/syzkaller/tree/master/pkg/report/testdata/linux/gu...
So thanks for persisting and questioning! We are getting better with each new test.
Thanks to you! I "complain" because I know you're so responsive. :)
Paolo
On 2019/12/05 19:22, Paolo Bonzini wrote:
Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of backtrace and I get to share syzkaller's joy every time. :)
This bisect result is bogus, though Tetsuo found the bug anyway. Perhaps you can exclude commits that only touch architectures other than x86?
It would be nice if coverage functionality can extract filenames in the source code and supply the list of filenames as arguments for bisect operation.
Also, (unrelated but) it would be nice if we can have "make yes2modconfig" target which converts CONFIG_FOO=y to CONFIG_FOO=m if FOO is tristate. syzbot is testing kernel configs close to "make allyesconfig" but I want to save kernel rebuild time by disabling unrelated functionality when manually "debug printk()ing" kernels.
On Thu, Dec 5, 2019 at 11:41 AM Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp wrote:
On 2019/12/05 19:22, Paolo Bonzini wrote:
Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of backtrace and I get to share syzkaller's joy every time. :)
This bisect result is bogus, though Tetsuo found the bug anyway. Perhaps you can exclude commits that only touch architectures other than x86?
It would be nice if coverage functionality can extract filenames in the source code and supply the list of filenames as arguments for bisect operation.
What is the criteria for file name extraction? What will bisect operation do with the set of files? If you have a feature/improvement request, please file it at: https://github.com/google/syzkaller/issues/new
On 2019/12/05 19:16, Dmitry Vyukov wrote:
On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini pbonzini@redhat.com wrote:
On 04/12/19 22:41, syzbot wrote:
syzbot has bisected this bug to:
commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 Author: Russell Currey ruscur@russell.cc Date: Mon Feb 8 04:08:20 2016 +0000
powerpc/powernv: Remove support for p5ioc2bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p.. git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b dashboard link: https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000
Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2")
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
Why is everybody being CC'd, even if the bug has nothing to do with the person's subsystem?
The To list should be intersection of 2 groups of emails: result of get_maintainers.pl on the file identified as culprit in the crash message + emails extracted from the bisected to commit.
There is "#syz uncc" command but it is too hard to utilize?
dri-devel@lists.freedesktop.org
-
Andrey Ryabinin -
Daniel Vetter -
Dmitry Vyukov -
Paolo Bonzini -
syzbot -
Tetsuo Handa