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: [email protected]
==================================================================
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 can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches
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=ebcbbb6576958a496500fee9cf7aa83ea00b5920
[2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000
[3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c9
Reported-by: syzbot <[email protected]>
Signed-off-by: Tetsuo Handa <[email protected]>
Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access")
Cc: George Kennedy <[email protected]>
---
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);
--
2.18.4
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=ebcbbb6576958a496500fee9cf7aa83ea00b5920
> [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000
> [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c9
>
> Reported-by: syzbot <[email protected]>
> Signed-off-by: Tetsuo Handa <[email protected]>
> Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access")
> Cc: George Kennedy <[email protected]>
> ---
> 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=ebcbbb6576958a496500fee9cf7aa83ea00b5920
> > [2] https://syzkaller.appspot.com/text?tag=Patch&x=14030853900000
> > [3] https://syzkaller.appspot.com/bug?id=6fba8c186d97cf1011ab17660e633b1cc4e080c9
> >
> > Reported-by: syzbot <[email protected]>
> > Signed-off-by: Tetsuo Handa <[email protected]>
> > Fixes: 39b3cffb8cf31117 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access")
> > Cc: George Kennedy <[email protected]>
> > ---
> > 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);
> >
> >
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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