Hello,
syzbot found the following issue on:
HEAD commit: 8eb858df Add linux-next specific files for 20200819 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1158a00e900000 kernel config: https://syzkaller.appspot.com/x/.config?x=cd187ef624ef7f02 dashboard link: https://syzkaller.appspot.com/bug?extid=b38b1ef6edf0c74a8d97 compiler: gcc (GCC) 10.1.0-syz 20200507 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=146a5589900000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=165aa636900000
IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+b38b1ef6edf0c74a8d97@syzkaller.appspotmail.com
================================================================== BUG: KASAN: global-out-of-bounds in fbcon_resize+0x781/0x810 drivers/video/fbdev/core/fbcon.c:2206 Read of size 4 at addr ffffffff8896d418 by task syz-executor732/6868
CPU: 0 PID: 6868 Comm: syz-executor732 Not tainted 5.9.0-rc1-next-20200819-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+0x18f/0x20d lib/dump_stack.c:118 print_address_description.constprop.0.cold+0x5/0x497 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 fbcon_resize+0x781/0x810 drivers/video/fbdev/core/fbcon.c:2206 resize_screen drivers/tty/vt/vt.c:1175 [inline] vc_do_resize+0x535/0x1150 drivers/tty/vt/vt.c:1246 vt_ioctl+0x11d2/0x2cc0 drivers/tty/vt/vt_ioctl.c:1025 tty_ioctl+0x1019/0x15f0 drivers/tty/tty_io.c:2656 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x440329 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 db 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffc8ff997d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440329 RDX: 0000000020000040 RSI: 0000000000005609 RDI: 0000000000000004 RBP: 00000000006ca018 R08: 000000000000000d R09: 00000000004002c8 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b90 R13: 0000000000401c20 R14: 0000000000000000 R15: 0000000000000000
The buggy address belongs to the variable: font_vga_8x16+0x58/0x60
Memory state around the buggy address: ffffffff8896d300: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 ffffffff8896d380: 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 00 f9 f9 f9
ffffffff8896d400: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
^ ffffffff8896d480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffffff8896d500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ==================================================================
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syzbot is reporting OOB read at fbcon_resize() [1], for commit 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") is by error using registered_fb[con2fb_map[vc->vc_num]]->fbcon_par->p->userfont (which was set to non-zero) instead of fb_display[vc->vc_num].userfont (which remains zero for that display).
We could remove tricky userfont flag [2], for we can determine it by comparing address of the font data and addresses of built-in font data. But since that commit is failing to fix the original OOB read [3], this patch keeps the change minimal in case we decide to revert altogether.
[1] https://syzkaller.appspot.com/bug?id=ebcbbb6576958a496500fee9cf7aa83ea00b592... [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000 [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c...
Reported-by: syzbot syzbot+b38b1ef6edf0c74a8d97@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") Cc: George Kennedy george.kennedy@oracle.com --- drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 66167830fefd..dae7ae7f225a 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2203,7 +2203,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width, struct fb_var_screeninfo var = info->var; int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh;
- if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) { + if (p->userfont && FNTSIZE(vc->vc_font.data)) { int size; int pitch = PITCH(vc->vc_font.width);
Greg, will you pick up this patch?
It seems that finding the real cause of [3] and actually fixing [3] will be difficult. Since I can't reproduce [3] locally, I will have to try flood of "#syz test" requests for debug printk() patches.
On 2020/09/11 7:57, Tetsuo Handa wrote:
syzbot is reporting OOB read at fbcon_resize() [1], for commit 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") is by error using registered_fb[con2fb_map[vc->vc_num]]->fbcon_par->p->userfont (which was set to non-zero) instead of fb_display[vc->vc_num].userfont (which remains zero for that display).
We could remove tricky userfont flag [2], for we can determine it by comparing address of the font data and addresses of built-in font data. But since that commit is failing to fix the original OOB read [3], this patch keeps the change minimal in case we decide to revert altogether.
[1] https://syzkaller.appspot.com/bug?id=ebcbbb6576958a496500fee9cf7aa83ea00b592... [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000 [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c...
Reported-by: syzbot syzbot+b38b1ef6edf0c74a8d97@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") Cc: George Kennedy george.kennedy@oracle.com
drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 66167830fefd..dae7ae7f225a 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2203,7 +2203,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width, struct fb_var_screeninfo var = info->var; int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh;
- if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) {
- if (p->userfont && FNTSIZE(vc->vc_font.data)) { int size; int pitch = PITCH(vc->vc_font.width);
On Wed, Sep 16, 2020 at 09:01:06AM +0900, Tetsuo Handa wrote:
Greg, will you pick up this patch?
It seems that finding the real cause of [3] and actually fixing [3] will be difficult. Since I can't reproduce [3] locally, I will have to try flood of "#syz test" requests for debug printk() patches.
Grasping for straws, but have you retested with the scrollback code removed already? That was full of fail and we outright deleted it:
50145474f6ef ("fbcon: remove soft scrollback code")
Cheers, Daniel
On 2020/09/11 7:57, Tetsuo Handa wrote:
syzbot is reporting OOB read at fbcon_resize() [1], for commit 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") is by error using registered_fb[con2fb_map[vc->vc_num]]->fbcon_par->p->userfont (which was set to non-zero) instead of fb_display[vc->vc_num].userfont (which remains zero for that display).
We could remove tricky userfont flag [2], for we can determine it by comparing address of the font data and addresses of built-in font data. But since that commit is failing to fix the original OOB read [3], this patch keeps the change minimal in case we decide to revert altogether.
[1] https://syzkaller.appspot.com/bug?id=ebcbbb6576958a496500fee9cf7aa83ea00b592... [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000 [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c...
Reported-by: syzbot syzbot+b38b1ef6edf0c74a8d97@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") Cc: George Kennedy george.kennedy@oracle.com
drivers/video/fbdev/core/fbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 66167830fefd..dae7ae7f225a 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2203,7 +2203,7 @@ static int fbcon_resize(struct vc_data *vc, unsigned int width, struct fb_var_screeninfo var = info->var; int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh;
- if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) {
- if (p->userfont && FNTSIZE(vc->vc_font.data)) { int size; int pitch = PITCH(vc->vc_font.width);
On Wed, Sep 16, 2020 at 09:01:06AM +0900, Tetsuo Handa wrote:
Greg, will you pick up this patch?
It seems that finding the real cause of [3] and actually fixing [3] will be difficult. Since I can't reproduce [3] locally, I will have to try flood of "#syz test" requests for debug printk() patches.
I agree with Daniel here, can you retest these against Linus's latest tree please?
thanks,
greg k-h
On 2020/09/16 17:26, Greg KH wrote:
On Wed, Sep 16, 2020 at 09:01:06AM +0900, Tetsuo Handa wrote:
Greg, will you pick up this patch?
It seems that finding the real cause of [3] and actually fixing [3] will be difficult. Since I can't reproduce [3] locally, I will have to try flood of "#syz test" requests for debug printk() patches.
I agree with Daniel here, can you retest these against Linus's latest tree please?
syzbot already reproduced these bugs using the latest commit. ;-)
You can find
ci-upstream-kasan-gce-root 2020/09/15 15:18 upstream fc4f28bb
record for "KASAN: global-out-of-bounds Read in bit_putcs" and
ci-upstream-kasan-gce-root 2020/09/16 09:54 upstream fc4f28bb
record for "KASAN: global-out-of-bounds Read in fbcon_resize".
On Wed, Sep 16, 2020 at 07:06:31PM +0900, Tetsuo Handa wrote:
On 2020/09/16 17:26, Greg KH wrote:
On Wed, Sep 16, 2020 at 09:01:06AM +0900, Tetsuo Handa wrote:
Greg, will you pick up this patch?
It seems that finding the real cause of [3] and actually fixing [3] will be difficult. Since I can't reproduce [3] locally, I will have to try flood of "#syz test" requests for debug printk() patches.
I agree with Daniel here, can you retest these against Linus's latest tree please?
syzbot already reproduced these bugs using the latest commit. ;-)
You can find
ci-upstream-kasan-gce-root 2020/09/15 15:18 upstream fc4f28bb
record for "KASAN: global-out-of-bounds Read in bit_putcs" and
ci-upstream-kasan-gce-root 2020/09/16 09:54 upstream fc4f28bb
record for "KASAN: global-out-of-bounds Read in fbcon_resize".
Ok, will pick it up now, thanks.
greg k-h
dri-devel@lists.freedesktop.org
-
Daniel Vetter -
Greg KH -
syzbot -
Tetsuo Handa -
Tetsuo Handa