WARNING in drm_mode_createblob_ioctl

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syzbot

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Oct 14, 2019, 2:09:09 AM10/14/19
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Hello,

syzbot found the following crash on:

HEAD commit: 8ada228a Add linux-next specific files for 20191011
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1423a87f600000
kernel config: https://syzkaller.appspot.com/x/.config?x=7cf4eed5fe42c31a
dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fb77e9...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 30449 at include/linux/thread_info.h:150
check_copy_size include/linux/thread_info.h:150 [inline]
WARNING: CPU: 1 PID: 30449 at include/linux/thread_info.h:150
copy_from_user include/linux/uaccess.h:143 [inline]
WARNING: CPU: 1 PID: 30449 at include/linux/thread_info.h:150
drm_mode_createblob_ioctl+0x398/0x490 drivers/gpu/drm/drm_property.c:800
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 30449 Comm: syz-executor.5 Not tainted 5.4.0-rc2-next-20191011
#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+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x35 kernel/panic.c:582
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
fixup_bug arch/x86/kernel/traps.c:169 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:check_copy_size include/linux/thread_info.h:150 [inline]
RIP: 0010:copy_from_user include/linux/uaccess.h:143 [inline]
RIP: 0010:drm_mode_createblob_ioctl+0x398/0x490
drivers/gpu/drm/drm_property.c:800
Code: c1 ea 03 80 3c 02 00 0f 85 ed 00 00 00 49 89 5d 00 e8 3c 28 cb fd 4c
89 f7 e8 64 92 9e 03 31 c0 e9 75 fd ff ff e8 28 28 cb fd <0f> 0b e8 21 28
cb fd 4d 85 e4 b8 f2 ff ff ff 0f 84 5b fd ff ff 89
RSP: 0018:ffff8880584efaa8 EFLAGS: 00010246
RAX: 0000000000040000 RBX: ffff8880a3a90000 RCX: ffffc900109da000
RDX: 0000000000040000 RSI: ffffffff83a7eaf8 RDI: 0000000000000007
RBP: ffff8880584efae8 R08: ffff888096c40080 R09: ffffed1014752110
R10: ffffed101475210f R11: ffff8880a3a9087f R12: ffffc90014907000
R13: ffff888028aa0000 R14: 000000009a6c7969 R15: ffffc90014907058


---
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 syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

Daniel Vetter

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Oct 14, 2019, 5:16:39 AM10/14/19
to syzbot, air...@linux.ie, dan...@ffwll.ch, dri-...@lists.freedesktop.org, linux-...@vger.kernel.org, maarten....@linux.intel.com, mri...@kernel.org, se...@poorly.run, syzkall...@googlegroups.com
On Sun, Oct 13, 2019 at 11:09:09PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 8ada228a Add linux-next specific files for 20191011
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1423a87f600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=7cf4eed5fe42c31a
> dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.

Hm only thing that could go wrong is how we allocate the target for the
user_copy, which is an argument directly from the ioctl parameter struct.
Does syzbot not track that? We use the standard linux ioctl struct
encoding in drm.

Otherwise I have no idea why it can't create a reliable reproducer for
this ... I'm also not seeing the bug, all the input validation we have
seems correct :-/
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

syzbot

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Oct 14, 2019, 5:39:42 AM10/14/19
to syzbot, air...@linux.ie, dri-...@lists.freedesktop.org, linux-...@vger.kernel.org, mri...@kernel.org, se...@poorly.run, syzkall...@googlegroups.com
Op 14-10-2019 om 11:16 schreef Daniel Vetter:
> On Sun, Oct 13, 2019 at 11:09:09PM -0700, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 8ada228a Add linux-next specific files for 20191011
>> git tree: linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=1423a87f600000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=7cf4eed5fe42c31a
>> dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
>> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>>
>> Unfortunately, I don't have any reproducer for this crash yet.
> Hm only thing that could go wrong is how we allocate the target for the
> user_copy, which is an argument directly from the ioctl parameter struct.
> Does syzbot not track that? We use the standard linux ioctl struct
> encoding in drm.
>
> Otherwise I have no idea why it can't create a reliable reproducer for
> this ... I'm also not seeing the bug, all the input validation we have
> seems correct :-/

I would like to see the entire dmesg?

in particular because it's likely WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count),

so I'd like to see the size it thinks for both..

Dmitry Vyukov

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Oct 14, 2019, 6:44:06 AM10/14/19
to syzbot, David Airlie, DRI, LKML, mri...@kernel.org, se...@poorly.run, syzkaller-bugs
On Mon, Oct 14, 2019 at 11:39 AM syzbot
<syzbot+fb77e9...@syzkaller.appspotmail.com> wrote:
>
> Op 14-10-2019 om 11:16 schreef Daniel Vetter:
> > On Sun, Oct 13, 2019 at 11:09:09PM -0700, syzbot wrote:
> >> Hello,
> >>
> >> syzbot found the following crash on:
> >>
> >> HEAD commit: 8ada228a Add linux-next specific files for 20191011
> >> git tree: linux-next
> >> console output: https://syzkaller.appspot.com/x/log.txt?x=1423a87f600000
> >> kernel config: https://syzkaller.appspot.com/x/.config?x=7cf4eed5fe42c31a
> >> dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
> >> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> >>
> >> Unfortunately, I don't have any reproducer for this crash yet.
> > Hm only thing that could go wrong is how we allocate the target for the
> > user_copy, which is an argument directly from the ioctl parameter struct.
> > Does syzbot not track that? We use the standard linux ioctl struct
> > encoding in drm.
> >
> > Otherwise I have no idea why it can't create a reliable reproducer for
> > this ... I'm also not seeing the bug, all the input validation we have
> > seems correct :-/
>
> I would like to see the entire dmesg?
>
> in particular because it's likely WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count),
>
> so I'd like to see the size it thinks for both..

And who are "you"? :) The email as if comes from syzbot:

From: syzbot <syzbot+fb77e9...@syzkaller.appspotmail.com>

But it is clearly not generated by syzbot code. Or is it some kind of
a glitch?...

Anyway, full console output is always referenced on every syzbot bug
report as "console output:" link.
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bug...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/67fb1a91-7ef3-9036-2d1b-877e394bcab2%40linux.intel.com.

syzbot

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Nov 6, 2019, 7:30:10 AM11/6/19
to air...@linux.ie, dan...@ffwll.ch, dri-...@lists.freedesktop.org, dvy...@google.com, linux-...@vger.kernel.org, maarten....@linux.intel.com, mri...@kernel.org, se...@poorly.run, syzkall...@googlegroups.com
syzbot has found a reproducer for the following crash on:

HEAD commit: 51309b9d Add linux-next specific files for 20191105
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13f5c078e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a9b1a641c1f1fc52
dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1212dc3ae00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145f604ae00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fb77e9...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 8842 at include/linux/thread_info.h:150
check_copy_size include/linux/thread_info.h:150 [inline]
WARNING: CPU: 0 PID: 8842 at include/linux/thread_info.h:150 copy_from_user
include/linux/uaccess.h:143 [inline]
WARNING: CPU: 0 PID: 8842 at include/linux/thread_info.h:150
drm_mode_createblob_ioctl+0x398/0x490 drivers/gpu/drm/drm_property.c:800
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 8842 Comm: syz-executor938 Not tainted 5.4.0-rc6-next-20191105
#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
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x35 kernel/panic.c:582
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
fixup_bug arch/x86/kernel/traps.c:169 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:check_copy_size include/linux/thread_info.h:150 [inline]
RIP: 0010:copy_from_user include/linux/uaccess.h:143 [inline]
RIP: 0010:drm_mode_createblob_ioctl+0x398/0x490
drivers/gpu/drm/drm_property.c:800
Code: c1 ea 03 80 3c 02 00 0f 85 ed 00 00 00 49 89 5d 00 e8 0c f2 c6 fd 4c
89 f7 e8 24 af aa 03 31 c0 e9 75 fd ff ff e8 f8 f1 c6 fd <0f> 0b e8 f1 f1
c6 fd 4d 85 e4 b8 f2 ff ff ff 0f 84 5b fd ff ff 89
RSP: 0018:ffff8880a5e07aa8 EFLAGS: 00010293
RAX: ffff88809f3a0440 RBX: ffff8880a387c000 RCX: ffffffff83ac75e2
RDX: 0000000000000000 RSI: ffffffff83ac77a8 RDI: 0000000000000007
RBP: ffff8880a5e07ae8 R08: ffff88809f3a0440 R09: ffffed101470f910
R10: ffffed101470f90f R11: ffff8880a387c87f R12: ffffc90005f5d000
R13: ffff8880a4d78000 R14: 0000000096e170d0 R15: ffffc90005f5d058
drm_ioctl_kernel+0x244/0x300 drivers/gpu/drm/drm_ioctl.c:786
drm_ioctl+0x54e/0xa60 drivers/gpu/drm/drm_ioctl.c:886
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/0x760 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x449659
Code: e8 fc b8 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 ab d6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6951f91db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dac38 RCX: 0000000000449659
RDX: 0000000020000000 RSI: ffffffffffffffbd RDI: 0000000000000004
RBP: 00000000006dac30 R08: 00007f6951f92700 R09: 0000000000000000
R10: 00007f6951f92700 R11: 0000000000000246 R12: 00000000006dac3c
R13: 00007ffeae0e7e9f R14: 00007f6951f929c0 R15: 20c49ba5e353f7cf
Kernel Offset: disabled
Rebooting in 86400 seconds..

syzbot

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Nov 6, 2019, 10:20:01 AM11/6/19
to air...@linux.ie, ak...@linux-foundation.org, dan...@ffwll.ch, dri-...@lists.freedesktop.org, dvy...@google.com, kees...@chromium.org, linux-...@vger.kernel.org, maarten....@linux.intel.com, mri...@kernel.org, se...@poorly.run, s...@canb.auug.org.au, syzkall...@googlegroups.com, vi...@zeniv.linux.org.uk
syzbot has bisected this bug to:

commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
Author: Kees Cook <kees...@chromium.org>
Date: Mon Nov 4 22:57:23 2019 +0000

uaccess: disallow > INT_MAX copy sizes

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=125fe6dce00000
start commit: 51309b9d Add linux-next specific files for 20191105
git tree: linux-next
final crash: https://syzkaller.appspot.com/x/report.txt?x=115fe6dce00000
console output: https://syzkaller.appspot.com/x/log.txt?x=165fe6dce00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a9b1a641c1f1fc52
dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1212dc3ae00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145f604ae00000

Reported-by: syzbot+fb77e9...@syzkaller.appspotmail.com
Fixes: 9e5a64c71b2f ("uaccess: disallow > INT_MAX copy sizes")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Daniel Vetter

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Nov 6, 2019, 10:28:58 AM11/6/19
to syzbot, Dave Airlie, Andrew Morton, dri-devel, Dmitry Vyukov, Kees Cook, Linux Kernel Mailing List, Maarten Lankhorst, Maxime Ripard, Sean Paul, Stephen Rothwell, syzkaller-bugs, Al Viro
On Wed, Nov 6, 2019 at 4:23 PM Daniel Vetter <dan...@ffwll.ch> wrote:
>
> On Wed, Nov 6, 2019 at 4:20 PM syzbot
> <syzbot+fb77e9...@syzkaller.appspotmail.com> wrote:
> >
> > syzbot has bisected this bug to:
> >
> > commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
> > Author: Kees Cook <kees...@chromium.org>
> > Date: Mon Nov 4 22:57:23 2019 +0000
> >
> > uaccess: disallow > INT_MAX copy sizes
>
> Ah cool, this explains it.
>
> fwiw I never managed to get the WARNING in the backtrace to lign up
> with any code. No idea what's been going on.

Ok I think I have an idea, the above commit isn't in the linux-next I
have here. Where is this from?
-Daniel

>
> I'll type a patch to paper over this.
> -Daniel
>
> >
> > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=125fe6dce00000
> > start commit: 51309b9d Add linux-next specific files for 20191105
> > git tree: linux-next
> > final crash: https://syzkaller.appspot.com/x/report.txt?x=115fe6dce00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=165fe6dce00000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=a9b1a641c1f1fc52
> > dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1212dc3ae00000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145f604ae00000
> >
> > Reported-by: syzbot+fb77e9...@syzkaller.appspotmail.com
> > Fixes: 9e5a64c71b2f ("uaccess: disallow > INT_MAX copy sizes")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch



--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Daniel Vetter

unread,
Nov 6, 2019, 10:30:28 AM11/6/19
to syzbot, Dave Airlie, Andrew Morton, dri-devel, Dmitry Vyukov, Kees Cook, Linux Kernel Mailing List, Maarten Lankhorst, Maxime Ripard, Sean Paul, Stephen Rothwell, syzkaller-bugs, Al Viro
On Wed, Nov 6, 2019 at 4:20 PM syzbot
<syzbot+fb77e9...@syzkaller.appspotmail.com> wrote:
>
> syzbot has bisected this bug to:
>
> commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
> Author: Kees Cook <kees...@chromium.org>
> Date: Mon Nov 4 22:57:23 2019 +0000
>
> uaccess: disallow > INT_MAX copy sizes

Ah cool, this explains it.

fwiw I never managed to get the WARNING in the backtrace to lign up
with any code. No idea what's been going on.

I'll type a patch to paper over this.
-Daniel

>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=125fe6dce00000
> start commit: 51309b9d Add linux-next specific files for 20191105
> git tree: linux-next
> final crash: https://syzkaller.appspot.com/x/report.txt?x=115fe6dce00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=165fe6dce00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a9b1a641c1f1fc52
> dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1212dc3ae00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145f604ae00000
>
> Reported-by: syzbot+fb77e9...@syzkaller.appspotmail.com
> Fixes: 9e5a64c71b2f ("uaccess: disallow > INT_MAX copy sizes")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection



Dmitry Vyukov

unread,
Nov 6, 2019, 10:33:24 AM11/6/19
to Daniel Vetter, syzbot, Dave Airlie, Andrew Morton, dri-devel, Kees Cook, Linux Kernel Mailing List, Maarten Lankhorst, Maxime Ripard, Sean Paul, Stephen Rothwell, syzkaller-bugs, Al Viro
On Wed, Nov 6, 2019 at 4:28 PM Daniel Vetter <dan...@ffwll.ch> wrote:
>
> On Wed, Nov 6, 2019 at 4:23 PM Daniel Vetter <dan...@ffwll.ch> wrote:
> >
> > On Wed, Nov 6, 2019 at 4:20 PM syzbot
> > <syzbot+fb77e9...@syzkaller.appspotmail.com> wrote:
> > >
> > > syzbot has bisected this bug to:
> > >
> > > commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
> > > Author: Kees Cook <kees...@chromium.org>
> > > Date: Mon Nov 4 22:57:23 2019 +0000
> > >
> > > uaccess: disallow > INT_MAX copy sizes
> >
> > Ah cool, this explains it.
> >
> > fwiw I never managed to get the WARNING in the backtrace to lign up
> > with any code. No idea what's been going on.
>
> Ok I think I have an idea, the above commit isn't in the linux-next I
> have here. Where is this from?
> -Daniel

You need to fetch tags to linux-next. syzbot started bisecting from
the commit where the crash happened, and it is now probably not the
current tag.

linux$ git show 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
Author: Kees Cook <kees...@chromium.org>
Date: Tue Nov 5 09:57:23 2019 +1100

uaccess: disallow > INT_MAX copy sizes

As we've done with VFS, string operations, etc, reject usercopy sizes
larger than INT_MAX, which would be nice to have for catching bugs related
to size calculation overflows[1].

This adds 10 bytes to x86_64 defconfig text and 1980 bytes to the data
section:

text data bss dec hex filename
19691167 5134320 1646664 26472151 193eed7 vmlinux.before
19691177 5136300 1646664 26474141 193f69d vmlinux.after

[1] https://marc.info/?l=linux-s390&m=156631939010493&w=2

Link: http://lkml.kernel.org/r/201908251612.F9902D7A@keescook
Signed-off-by: Kees Cook <kees...@chromium.org>
Suggested-by: Dan Carpenter <dan.ca...@oracle.com>
Cc: Alexander Viro <vi...@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <ak...@linux-foundation.org>
Signed-off-by: Stephen Rothwell <s...@canb.auug.org.au>

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 659a4400517b2..e93e249a4e9bf 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -147,6 +147,8 @@ check_copy_size(const void *addr, size_t bytes,
bool is_source)
__bad_copy_to();
return false;
}
+ if (WARN_ON_ONCE(bytes > INT_MAX))
+ return false;
check_object_size(addr, bytes, is_source);
return true;

Dmitry Vyukov

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Nov 6, 2019, 10:36:57 AM11/6/19
to Daniel Vetter, syzbot, Dave Airlie, Andrew Morton, dri-devel, Kees Cook, Linux Kernel Mailing List, Maarten Lankhorst, Maxime Ripard, Sean Paul, Stephen Rothwell, syzkaller-bugs, Al Viro
On Wed, Nov 6, 2019 at 4:30 PM Daniel Vetter <dan...@ffwll.ch> wrote:
>
> On Wed, Nov 6, 2019 at 4:20 PM syzbot
> <syzbot+fb77e9...@syzkaller.appspotmail.com> wrote:
> >
> > syzbot has bisected this bug to:
> >
> > commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
> > Author: Kees Cook <kees...@chromium.org>
> > Date: Mon Nov 4 22:57:23 2019 +0000
> >
> > uaccess: disallow > INT_MAX copy sizes
>
> Ah cool, this explains it.
>
> fwiw I never managed to get the WARNING in the backtrace to lign up
> with any code. No idea what's been going on.
>
> I'll type a patch to paper over this.
> -Daniel

If I get:
git checkout 8ada228a
then include/linux/thread_info.h:150
points right to:
if (WARN_ON_ONCE(bytes > INT_MAX))

Is the size user-controllable here?


> >
> > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=125fe6dce00000
> > start commit: 51309b9d Add linux-next specific files for 20191105
> > git tree: linux-next
> > final crash: https://syzkaller.appspot.com/x/report.txt?x=115fe6dce00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=165fe6dce00000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=a9b1a641c1f1fc52
> > dashboard link: https://syzkaller.appspot.com/bug?extid=fb77e97ebf0612ee6914
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1212dc3ae00000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145f604ae00000
> >
> > Reported-by: syzbot+fb77e9...@syzkaller.appspotmail.com
> > Fixes: 9e5a64c71b2f ("uaccess: disallow > INT_MAX copy sizes")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>
> --
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Daniel Vetter

unread,
Nov 6, 2019, 10:57:05 AM11/6/19
to Dmitry Vyukov, syzbot, Dave Airlie, Andrew Morton, dri-devel, Kees Cook, Linux Kernel Mailing List, Maarten Lankhorst, Maxime Ripard, Sean Paul, Stephen Rothwell, syzkaller-bugs, Al Viro
On Wed, Nov 6, 2019 at 4:33 PM Dmitry Vyukov <dvy...@google.com> wrote:
>
> On Wed, Nov 6, 2019 at 4:28 PM Daniel Vetter <dan...@ffwll.ch> wrote:
> >
> > On Wed, Nov 6, 2019 at 4:23 PM Daniel Vetter <dan...@ffwll.ch> wrote:
> > >
> > > On Wed, Nov 6, 2019 at 4:20 PM syzbot
> > > <syzbot+fb77e9...@syzkaller.appspotmail.com> wrote:
> > > >
> > > > syzbot has bisected this bug to:
> > > >
> > > > commit 9e5a64c71b2f70ba530f8156046dd7dfb8a7a0ba
> > > > Author: Kees Cook <kees...@chromium.org>
> > > > Date: Mon Nov 4 22:57:23 2019 +0000
> > > >
> > > > uaccess: disallow > INT_MAX copy sizes
> > >
> > > Ah cool, this explains it.
> > >
> > > fwiw I never managed to get the WARNING in the backtrace to lign up
> > > with any code. No idea what's been going on.
> >
> > Ok I think I have an idea, the above commit isn't in the linux-next I
> > have here. Where is this from?
> > -Daniel
>
> You need to fetch tags to linux-next. syzbot started bisecting from
> the commit where the crash happened, and it is now probably not the
> current tag.

Indeed it's an -mm patch so rebases every day. I tried looking for it,
but found nothing, not sure what exactly I screwed up. Patch on the
way.
-Daniel
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