Hello,
Triggered this while fuzzing v3.17-rc1-51-g372b1db with Trinity.
Tommi
[drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format divide error: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 0 PID: 2854 Comm: trinity-c7 Not tainted 3.17.0-rc1+ #14 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 task: ffff88003926cac0 ti: ffff8800356b4000 task.ti: ffff8800356b4000 RIP: 0010:[<ffffffff816688e3>] [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0 RSP: 0018:ffff8800356b7dc0 EFLAGS: 00010246 RAX: 00000000ffffffff RBX: ffff88003545da68 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff8800356b7e18 RDI: ffff88003d5c67b0 RBP: ffff8800356b7dc8 R08: 0000000000000000 R09: 00000000ffffffff R10: 00000000ffffffff R11: ffffffff817f6d30 R12: 00000000000000b2 R13: fffffffffffffff2 R14: ffff88003d5c67b0 R15: ffff88003545da68 FS: 00007f06208fa700(0000) GS:ffff88003fa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001903108 CR3: 0000000036efa000 CR4: 00000000000006f0 Stack: ffff8800356b7e18 ffff8800356b7ec8 ffffffff8165ac60 ffff8800356b7df8 ffff8800356b7e18 ffff8800356b7e18 ffffffff824e1440 0000000000d52000 0000000000000020 00000000c02064b2 00000000fffffff2 ffffffffffffffff Call Trace: [<ffffffff8165ac60>] drm_ioctl+0x3b0/0x640 [<ffffffff814b81b8>] ? avc_has_perm+0x218/0x2f0 [<ffffffff814b7fc0>] ? avc_has_perm+0x20/0x2f0 [<ffffffff81170bb8>] ? sched_clock_cpu+0xa8/0xf0 [<ffffffff812922a0>] do_vfs_ioctl+0x4d0/0x510 [<ffffffff814ba745>] ? selinux_file_ioctl+0xf5/0x100 [<ffffffff8129232e>] SyS_ioctl+0x4e/0x80 [<ffffffff822b10e9>] system_call_fastpath+0x16/0x1b Code: 55 41 b9 ff ff ff ff 41 83 c0 07 44 89 c8 41 c1 e8 03 48 89 e5 53 48 89 d3 31 d2 f7 f1 41 39 c0 77 46 41 0f af c8 31 d2 44 89 c8 <f7> f1 41 39 c2 77 36 41 0f af ca b8 ea ff ff ff 81 c1 ff 0f 00 RIP [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0 RSP <ffff8800356b7dc0> ---[ end trace 6919129b71d9bf98 ]--- [drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format
(gdb) list *0xffffffff816688e3 0xffffffff816688e3 is in drm_mode_create_dumb_ioctl (drivers/gpu/drm/drm_crtc.c:4703). 4698 /* overflow checks for 32bit size calculations */ 4699 cpp = DIV_ROUND_UP(args->bpp, 8); 4700 if (cpp > 0xffffffffU / args->width) 4701 return -EINVAL; 4702 stride = cpp * args->width; 4703 if (args->height > 0xffffffffU / stride) 4704 return -EINVAL; 4705 4706 /* test for wrap-around */ 4707 size = args->height * stride; (gdb) disassemble drm_mode_create_dumb_ioctl Dump of assembler code for function drm_mode_create_dumb_ioctl: 0xffffffff81668890 <+0>: mov 0x20(%rdi),%rax 0xffffffff81668894 <+4>: mov 0x160(%rax),%r11 0xffffffff8166889b <+11>: test %r11,%r11 0xffffffff8166889e <+14>: je 0xffffffff8166890f <drm_mode_create_dumb_ioctl+127> 0xffffffff816688a0 <+16>: mov 0x4(%rsi),%ecx 0xffffffff816688a3 <+19>: test %ecx,%ecx 0xffffffff816688a5 <+21>: je 0xffffffff81668918 <drm_mode_create_dumb_ioctl+136> 0xffffffff816688a7 <+23>: mov (%rsi),%r10d 0xffffffff816688aa <+26>: test %r10d,%r10d 0xffffffff816688ad <+29>: je 0xffffffff81668918 <drm_mode_create_dumb_ioctl+136> 0xffffffff816688af <+31>: mov 0x8(%rsi),%r8d 0xffffffff816688b3 <+35>: test %r8d,%r8d 0xffffffff816688b6 <+38>: je 0xffffffff81668918 <drm_mode_create_dumb_ioctl+136> 0xffffffff816688b8 <+40>: push %rbp 0xffffffff816688b9 <+41>: mov $0xffffffff,%r9d 0xffffffff816688bf <+47>: add $0x7,%r8d 0xffffffff816688c3 <+51>: mov %r9d,%eax 0xffffffff816688c6 <+54>: shr $0x3,%r8d 0xffffffff816688ca <+58>: mov %rsp,%rbp 0xffffffff816688cd <+61>: push %rbx 0xffffffff816688ce <+62>: mov %rdx,%rbx 0xffffffff816688d1 <+65>: xor %edx,%edx 0xffffffff816688d3 <+67>: div %ecx 0xffffffff816688d5 <+69>: cmp %eax,%r8d 0xffffffff816688d8 <+72>: ja 0xffffffff81668920 <drm_mode_create_dumb_ioctl+144> 0xffffffff816688da <+74>: imul %r8d,%ecx 0xffffffff816688de <+78>: xor %edx,%edx 0xffffffff816688e0 <+80>: mov %r9d,%eax 0xffffffff816688e3 <+83>: div %ecx 0xffffffff816688e5 <+85>: cmp %eax,%r10d 0xffffffff816688e8 <+88>: ja 0xffffffff81668920 <drm_mode_create_dumb_ioctl+144> 0xffffffff816688ea <+90>: imul %r10d,%ecx 0xffffffff816688ee <+94>: mov $0xffffffea,%eax 0xffffffff816688f3 <+99>: add $0xfff,%ecx 0xffffffff816688f9 <+105>: and $0xfffff000,%ecx 0xffffffff816688ff <+111>: je 0xffffffff81668928 <drm_mode_create_dumb_ioctl+152> 0xffffffff81668901 <+113>: mov %rsi,%rdx 0xffffffff81668904 <+116>: mov %rdi,%rsi 0xffffffff81668907 <+119>: mov %rbx,%rdi 0xffffffff8166890a <+122>: callq *%r11 0xffffffff8166890d <+125>: jmp 0xffffffff81668928 <drm_mode_create_dumb_ioctl+152> 0xffffffff8166890f <+127>: mov $0xffffffda,%eax 0xffffffff81668914 <+132>: retq 0xffffffff81668915 <+133>: nopl (%rax) 0xffffffff81668918 <+136>: mov $0xffffffea,%eax 0xffffffff8166891d <+141>: retq 0xffffffff8166891e <+142>: xchg %ax,%ax 0xffffffff81668920 <+144>: mov $0xffffffea,%eax 0xffffffff81668925 <+149>: nopl (%rax) 0xffffffff81668928 <+152>: pop %rbx 0xffffffff81668929 <+153>: pop %rbp 0xffffffff8166892a <+154>: retq End of assembler dump. (gdb)
Hi
On Thu, Aug 21, 2014 at 8:18 PM, Tommi Rantala tt.rantala@gmail.com wrote:
Hello,
Triggered this while fuzzing v3.17-rc1-51-g372b1db with Trinity.
Tommi
[drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format divide error: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 0 PID: 2854 Comm: trinity-c7 Not tainted 3.17.0-rc1+ #14 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 task: ffff88003926cac0 ti: ffff8800356b4000 task.ti: ffff8800356b4000 RIP: 0010:[<ffffffff816688e3>] [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0 RSP: 0018:ffff8800356b7dc0 EFLAGS: 00010246 RAX: 00000000ffffffff RBX: ffff88003545da68 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff8800356b7e18 RDI: ffff88003d5c67b0 RBP: ffff8800356b7dc8 R08: 0000000000000000 R09: 00000000ffffffff R10: 00000000ffffffff R11: ffffffff817f6d30 R12: 00000000000000b2 R13: fffffffffffffff2 R14: ffff88003d5c67b0 R15: ffff88003545da68 FS: 00007f06208fa700(0000) GS:ffff88003fa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001903108 CR3: 0000000036efa000 CR4: 00000000000006f0 Stack: ffff8800356b7e18 ffff8800356b7ec8 ffffffff8165ac60 ffff8800356b7df8 ffff8800356b7e18 ffff8800356b7e18 ffffffff824e1440 0000000000d52000 0000000000000020 00000000c02064b2 00000000fffffff2 ffffffffffffffff Call Trace: [<ffffffff8165ac60>] drm_ioctl+0x3b0/0x640 [<ffffffff814b81b8>] ? avc_has_perm+0x218/0x2f0 [<ffffffff814b7fc0>] ? avc_has_perm+0x20/0x2f0 [<ffffffff81170bb8>] ? sched_clock_cpu+0xa8/0xf0 [<ffffffff812922a0>] do_vfs_ioctl+0x4d0/0x510 [<ffffffff814ba745>] ? selinux_file_ioctl+0xf5/0x100 [<ffffffff8129232e>] SyS_ioctl+0x4e/0x80 [<ffffffff822b10e9>] system_call_fastpath+0x16/0x1b Code: 55 41 b9 ff ff ff ff 41 83 c0 07 44 89 c8 41 c1 e8 03 48 89 e5 53 48 89 d3 31 d2 f7 f1 41 39 c0 77 46 41 0f af c8 31 d2 44 89 c8 <f7> f1 41 39 c2 77 36 41 0f af ca b8 ea ff ff ff 81 c1 ff 0f 00 RIP [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0 RSP <ffff8800356b7dc0> ---[ end trace 6919129b71d9bf98 ]--- [drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format
(gdb) list *0xffffffff816688e3 0xffffffff816688e3 is in drm_mode_create_dumb_ioctl (drivers/gpu/drm/drm_crtc.c:4703). 4698 /* overflow checks for 32bit size calculations */ 4699 cpp = DIV_ROUND_UP(args->bpp, 8); 4700 if (cpp > 0xffffffffU / args->width) 4701 return -EINVAL; 4702 stride = cpp * args->width; 4703 if (args->height > 0xffffffffU / stride) 4704 return -EINVAL;
Hm, this doesn't make sense to me. args->bpp/width/height are guaranteed to be non-zero and 32bit. Therefore, DIV_ROUND_UP() cannot return 0 and "cpp" is thus non-zero. The overflow check makes sure "cpp * args->width" cannot overflow, both are non-zero so "stride" is non-zero and valid.
I cannot make much sense out of the x86 assembly below, so help welcome.
Thanks David
4705 4706 /* test for wrap-around */ 4707 size = args->height * stride; (gdb) disassemble drm_mode_create_dumb_ioctl Dump of assembler code for function drm_mode_create_dumb_ioctl: 0xffffffff81668890 <+0>: mov 0x20(%rdi),%rax 0xffffffff81668894 <+4>: mov 0x160(%rax),%r11 0xffffffff8166889b <+11>: test %r11,%r11 0xffffffff8166889e <+14>: je 0xffffffff8166890f <drm_mode_create_dumb_ioctl+127> 0xffffffff816688a0 <+16>: mov 0x4(%rsi),%ecx 0xffffffff816688a3 <+19>: test %ecx,%ecx 0xffffffff816688a5 <+21>: je 0xffffffff81668918 <drm_mode_create_dumb_ioctl+136> 0xffffffff816688a7 <+23>: mov (%rsi),%r10d 0xffffffff816688aa <+26>: test %r10d,%r10d 0xffffffff816688ad <+29>: je 0xffffffff81668918 <drm_mode_create_dumb_ioctl+136> 0xffffffff816688af <+31>: mov 0x8(%rsi),%r8d 0xffffffff816688b3 <+35>: test %r8d,%r8d 0xffffffff816688b6 <+38>: je 0xffffffff81668918 <drm_mode_create_dumb_ioctl+136> 0xffffffff816688b8 <+40>: push %rbp 0xffffffff816688b9 <+41>: mov $0xffffffff,%r9d 0xffffffff816688bf <+47>: add $0x7,%r8d 0xffffffff816688c3 <+51>: mov %r9d,%eax 0xffffffff816688c6 <+54>: shr $0x3,%r8d 0xffffffff816688ca <+58>: mov %rsp,%rbp 0xffffffff816688cd <+61>: push %rbx 0xffffffff816688ce <+62>: mov %rdx,%rbx 0xffffffff816688d1 <+65>: xor %edx,%edx 0xffffffff816688d3 <+67>: div %ecx 0xffffffff816688d5 <+69>: cmp %eax,%r8d 0xffffffff816688d8 <+72>: ja 0xffffffff81668920 <drm_mode_create_dumb_ioctl+144> 0xffffffff816688da <+74>: imul %r8d,%ecx 0xffffffff816688de <+78>: xor %edx,%edx 0xffffffff816688e0 <+80>: mov %r9d,%eax 0xffffffff816688e3 <+83>: div %ecx 0xffffffff816688e5 <+85>: cmp %eax,%r10d 0xffffffff816688e8 <+88>: ja 0xffffffff81668920 <drm_mode_create_dumb_ioctl+144> 0xffffffff816688ea <+90>: imul %r10d,%ecx 0xffffffff816688ee <+94>: mov $0xffffffea,%eax 0xffffffff816688f3 <+99>: add $0xfff,%ecx 0xffffffff816688f9 <+105>: and $0xfffff000,%ecx 0xffffffff816688ff <+111>: je 0xffffffff81668928 <drm_mode_create_dumb_ioctl+152> 0xffffffff81668901 <+113>: mov %rsi,%rdx 0xffffffff81668904 <+116>: mov %rdi,%rsi 0xffffffff81668907 <+119>: mov %rbx,%rdi 0xffffffff8166890a <+122>: callq *%r11 0xffffffff8166890d <+125>: jmp 0xffffffff81668928 <drm_mode_create_dumb_ioctl+152> 0xffffffff8166890f <+127>: mov $0xffffffda,%eax 0xffffffff81668914 <+132>: retq 0xffffffff81668915 <+133>: nopl (%rax) 0xffffffff81668918 <+136>: mov $0xffffffea,%eax 0xffffffff8166891d <+141>: retq 0xffffffff8166891e <+142>: xchg %ax,%ax 0xffffffff81668920 <+144>: mov $0xffffffea,%eax 0xffffffff81668925 <+149>: nopl (%rax) 0xffffffff81668928 <+152>: pop %rbx 0xffffffff81668929 <+153>: pop %rbp 0xffffffff8166892a <+154>: retq End of assembler dump. (gdb)
22.8.2014 13.38 kirjoitti "David Herrmann" dh.herrmann@gmail.com:
Hi
On Thu, Aug 21, 2014 at 8:18 PM, Tommi Rantala tt.rantala@gmail.com wrote:
Hello,
Triggered this while fuzzing v3.17-rc1-51-g372b1db with Trinity.
Tommi
[drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format divide error: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 0 PID: 2854 Comm: trinity-c7 Not tainted 3.17.0-rc1+ #14 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 task: ffff88003926cac0 ti: ffff8800356b4000 task.ti: ffff8800356b4000 RIP: 0010:[<ffffffff816688e3>] [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0 RSP: 0018:ffff8800356b7dc0 EFLAGS: 00010246 RAX: 00000000ffffffff RBX: ffff88003545da68 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff8800356b7e18 RDI: ffff88003d5c67b0 RBP: ffff8800356b7dc8 R08: 0000000000000000 R09: 00000000ffffffff R10: 00000000ffffffff R11: ffffffff817f6d30 R12: 00000000000000b2 R13: fffffffffffffff2 R14: ffff88003d5c67b0 R15: ffff88003545da68 FS: 00007f06208fa700(0000) GS:ffff88003fa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001903108 CR3: 0000000036efa000 CR4: 00000000000006f0 Stack: ffff8800356b7e18 ffff8800356b7ec8 ffffffff8165ac60 ffff8800356b7df8 ffff8800356b7e18 ffff8800356b7e18 ffffffff824e1440 0000000000d52000 0000000000000020 00000000c02064b2 00000000fffffff2 ffffffffffffffff Call Trace: [<ffffffff8165ac60>] drm_ioctl+0x3b0/0x640 [<ffffffff814b81b8>] ? avc_has_perm+0x218/0x2f0 [<ffffffff814b7fc0>] ? avc_has_perm+0x20/0x2f0 [<ffffffff81170bb8>] ? sched_clock_cpu+0xa8/0xf0 [<ffffffff812922a0>] do_vfs_ioctl+0x4d0/0x510 [<ffffffff814ba745>] ? selinux_file_ioctl+0xf5/0x100 [<ffffffff8129232e>] SyS_ioctl+0x4e/0x80 [<ffffffff822b10e9>] system_call_fastpath+0x16/0x1b Code: 55 41 b9 ff ff ff ff 41 83 c0 07 44 89 c8 41 c1 e8 03 48 89 e5 53 48 89 d3 31 d2 f7 f1 41 39 c0 77 46 41 0f af c8 31 d2 44 89 c8 <f7> f1 41 39 c2 77 36 41 0f af ca b8 ea ff ff ff 81 c1 ff 0f 00 RIP [<ffffffff816688e3>] drm_mode_create_dumb_ioctl+0x53/0xa0 RSP <ffff8800356b7dc0> ---[ end trace 6919129b71d9bf98 ]--- [drm:drm_mode_legacy_fb_format] *ERROR* bad bpp, assuming x8r8g8b8 pixel format
(gdb) list *0xffffffff816688e3 0xffffffff816688e3 is in drm_mode_create_dumb_ioctl (drivers/gpu/drm/drm_crtc.c:4703). 4698 /* overflow checks for 32bit size calculations */ 4699 cpp = DIV_ROUND_UP(args->bpp, 8); 4700 if (cpp > 0xffffffffU / args->width) 4701 return -EINVAL; 4702 stride = cpp * args->width; 4703 if (args->height > 0xffffffffU / stride) 4704 return -EINVAL;
Hm, this doesn't make sense to me. args->bpp/width/height are guaranteed to be non-zero and 32bit. Therefore, DIV_ROUND_UP() cannot return 0 and "cpp" is thus non-zero. The overflow check makes sure "cpp * args->width" cannot overflow, both are non-zero so "stride" is non-zero and valid.
I cannot make much sense out of the x86 assembly below, so help welcome.
Hi David,
I put a BUG_ON(stride==0), and it is indeed crashing due to stride being zero.
I tried to get the variables with gdb since I'm running the kernel in qemu, but for whatever reason the breakpoints do not seem to always have any effect, IOW the execution blasts right through the breakpoints.
Finally I did get one instance where the breakpoint would trigger, and gdb told me this. Does it make sense?
(gdb) bt #0 drm_mode_create_dumb_ioctl (dev=0xffff88003d634520, data=0xffff880034837e18, file_priv=0xffff8800361faa40) at drivers/gpu/drm/drm_crtc.c:4704 #1 0xffffffff8165ad20 in drm_ioctl (filp=<optimized out>, cmd=<optimized out>, arg=<optimized out>) at drivers/gpu/drm/drm_ioctl.c:727 #2 0xffffffff812922a0 in vfs_ioctl (arg=<optimized out>, cmd=<optimized out>, filp=<optimized out>) at fs/ioctl.c:43 #3 do_vfs_ioctl (filp=0xffff88003d634520, fd=36, cmd=<optimized out>, arg=<optimized out>) at fs/ioctl.c:598 #4 0xffffffff8129232e in SYSC_ioctl (arg=<optimized out>, cmd=<optimized out>, fd=<optimized out>) at fs/ioctl.c:613 #5 SyS_ioctl (fd=36, cmd=3223348402, arg=9592832) at fs/ioctl.c:604 #6 <signal handler called> #7 0x00007f69a2b0eb69 in ?? () #8 0xdead4ead6b6b0e0e in ?? () #9 0x6b6b6b6bffffffff in ?? () #10 0xffffffffffffffff in ?? () #11 0xffffffff840ba810 in ?? () #12 0xffffffff838a9e70 in lock_classes () #13 0xffffffff83924540 in lock_classes () #14 0xffffffff828ed4ef in kallsyms_token_index () #15 0x6b6b6b6b00000000 in ?? () #16 0xffffffff81279ec8 in kmemleak_scan () at mm/kmemleak.c:1410 Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) print *args value has been optimized out
(gdb) info locals cpp = 0 stride = 0 size = <optimized out>
(gdb) print /x *(struct drm_mode_create_dumb *)data $13 = { height = 0xffffffff, width = 0xffffffff, bpp = 0xffffffff, flags = 0xffffffff, handle = 0xffffffff, pitch = 0xffffffff, size = 0xffffffffffffffff }
Tommi
Hi
On Sun, Aug 24, 2014 at 7:12 PM, Tommi Rantala tt.rantala@gmail.com wrote:
(gdb) info locals cpp = 0 stride = 0 size = <optimized out>
(gdb) print /x *(struct drm_mode_create_dumb *)data $13 = { height = 0xffffffff, width = 0xffffffff, bpp = 0xffffffff, flags = 0xffffffff, handle = 0xffffffff, pitch = 0xffffffff, size = 0xffffffffffffffff }
Thanks a lot for digging into this. Looks like DIV_ROUND_UP() can overflow... *check* Yes, it's defined as: #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
Kinda unexpected that a function called "DIV" can overflow, but makes sense here. Obvious fix is to test "cpp" for zero. I will send it to dri-devel.
Thanks! David
dri-devel@lists.freedesktop.org