* Re: INFO: rcu detected stall in sys_sendfile64 (2)
[not found] <00000000000010b2fc057fcdfaba@google.com>
@ 2019-03-12 3:59 ` syzbot
2019-03-12 4:08 ` Al Viro
0 siblings, 1 reply; 5+ messages in thread
From: syzbot @ 2019-03-12 3:59 UTC (permalink / raw)
To: airlied, akpm, amir73il, chris, darrick.wong, david, dri-devel,
dvyukov, eparis, hannes, hughd, intel-gfx, jack, jani.nikula,
joonas.lahtinen, jrdr.linux, linux-kernel, linux-mm, mingo,
mszeredi, penguin-kernel, peterz, rodrigo.vivi, syzkaller-bugs,
viro, willy
syzbot has bisected this bug to:
commit 34e07e42c55aeaa78e93b057a6664e2ecde3fadb
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu Feb 8 10:54:48 2018 +0000
drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13220283200000
start commit: 34e07e42 drm/i915: Add missing kerneldoc for 'ent' in i915..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=10a20283200000
console output: https://syzkaller.appspot.com/x/log.txt?x=17220283200000
kernel config: https://syzkaller.appspot.com/x/.config?x=abc3dc9b7a900258
dashboard link: https://syzkaller.appspot.com/bug?extid=1505c80c74256c6118a5
userspace arch: amd64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12c4dc28c00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15df4108c00000
Reported-by: syzbot+1505c80c74256c6118a5@syzkaller.appspotmail.com
Fixes: 34e07e42 ("drm/i915: Add missing kerneldoc for 'ent' in
i915_driver_init_early")
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: INFO: rcu detected stall in sys_sendfile64 (2)
2019-03-12 3:59 ` INFO: rcu detected stall in sys_sendfile64 (2) syzbot
@ 2019-03-12 4:08 ` Al Viro
2019-03-12 8:00 ` Jani Nikula
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Al Viro @ 2019-03-12 4:08 UTC (permalink / raw)
To: syzbot
Cc: airlied, akpm, amir73il, chris, darrick.wong, david, dri-devel,
dvyukov, eparis, hannes, hughd, intel-gfx, jack, jani.nikula,
joonas.lahtinen, jrdr.linux, linux-kernel, linux-mm, mingo,
mszeredi, penguin-kernel, peterz, rodrigo.vivi, syzkaller-bugs,
willy
On Mon, Mar 11, 2019 at 08:59:00PM -0700, syzbot wrote:
> syzbot has bisected this bug to:
>
> commit 34e07e42c55aeaa78e93b057a6664e2ecde3fadb
> Author: Chris Wilson <chris@chris-wilson.co.uk>
> Date: Thu Feb 8 10:54:48 2018 +0000
>
> drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13220283200000
> start commit: 34e07e42 drm/i915: Add missing kerneldoc for 'ent' in i915..
> git tree: upstream
> final crash: https://syzkaller.appspot.com/x/report.txt?x=10a20283200000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17220283200000
> kernel config: https://syzkaller.appspot.com/x/.config?x=abc3dc9b7a900258
> dashboard link: https://syzkaller.appspot.com/bug?extid=1505c80c74256c6118a5
> userspace arch: amd64
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12c4dc28c00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15df4108c00000
>
> Reported-by: syzbot+1505c80c74256c6118a5@syzkaller.appspotmail.com
> Fixes: 34e07e42 ("drm/i915: Add missing kerneldoc for 'ent' in
> i915_driver_init_early")
Umm... Might be a good idea to add some plausibility filters - it is,
in theory, possible that adding a line in a comment changes behaviour
(without compiler bugs, even - playing with __LINE__ is all it would
take), but the odds that it's _not_ a false positive are very low.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: INFO: rcu detected stall in sys_sendfile64 (2)
2019-03-12 4:08 ` Al Viro
@ 2019-03-12 8:00 ` Jani Nikula
2019-03-12 14:29 ` Tetsuo Handa
2019-03-12 17:10 ` Dmitry Vyukov
2 siblings, 0 replies; 5+ messages in thread
From: Jani Nikula @ 2019-03-12 8:00 UTC (permalink / raw)
To: Al Viro, syzbot
Cc: jack, penguin-kernel, david, dri-devel, linux-mm, darrick.wong,
hughd, willy, airlied, mingo, mszeredi, amir73il, intel-gfx,
syzkaller-bugs, rodrigo.vivi, dvyukov, linux-kernel, eparis,
peterz, jrdr.linux, hannes, akpm
On Tue, 12 Mar 2019, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Mon, Mar 11, 2019 at 08:59:00PM -0700, syzbot wrote:
>> syzbot has bisected this bug to:
>>
>> commit 34e07e42c55aeaa78e93b057a6664e2ecde3fadb
>> Author: Chris Wilson <chris@chris-wilson.co.uk>
>> Date: Thu Feb 8 10:54:48 2018 +0000
>>
>> drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early
>>
>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13220283200000
>> start commit: 34e07e42 drm/i915: Add missing kerneldoc for 'ent' in i915..
>> git tree: upstream
>> final crash: https://syzkaller.appspot.com/x/report.txt?x=10a20283200000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=17220283200000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=abc3dc9b7a900258
>> dashboard link: https://syzkaller.appspot.com/bug?extid=1505c80c74256c6118a5
>> userspace arch: amd64
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12c4dc28c00000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15df4108c00000
>>
>> Reported-by: syzbot+1505c80c74256c6118a5@syzkaller.appspotmail.com
>> Fixes: 34e07e42 ("drm/i915: Add missing kerneldoc for 'ent' in
>> i915_driver_init_early")
>
> Umm... Might be a good idea to add some plausibility filters - it is,
> in theory, possible that adding a line in a comment changes behaviour
> (without compiler bugs, even - playing with __LINE__ is all it would
> take), but the odds that it's _not_ a false positive are very low.
If it's not a false positive, it's bound to be good source material for
IOCCC.
BR,
Jani.
--
Jani Nikula, Intel Open Source Graphics Center
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: INFO: rcu detected stall in sys_sendfile64 (2)
2019-03-12 4:08 ` Al Viro
2019-03-12 8:00 ` Jani Nikula
@ 2019-03-12 14:29 ` Tetsuo Handa
2019-03-12 17:10 ` Dmitry Vyukov
2 siblings, 0 replies; 5+ messages in thread
From: Tetsuo Handa @ 2019-03-12 14:29 UTC (permalink / raw)
To: syzbot, dvyukov, syzkaller-bugs; +Cc: Al Viro, linux-kernel
(Moving most recipients to bcc: in order to avoid flooding.)
On 2019/03/12 13:08, Al Viro wrote:
> Umm... Might be a good idea to add some plausibility filters - it is,
> in theory, possible that adding a line in a comment changes behaviour
> (without compiler bugs, even - playing with __LINE__ is all it would
> take), but the odds that it's _not_ a false positive are very low.
Well, 108 out of 168 tests done during this bisection failed to test.
With such high failure ratio, it is possible that by chance no crash
happened during few tests for specific commit; causing a wrong bisection
result. I expect that when trying to conclude "git bisect good" for
specific commit, the tests should be repeated until no crash happened
during 8 successful tests.
Also, this bisection is finding multiple different crash patterns, which
suggests that the crashed tests are not giving correct feedback to syzbot.
$ grep -F 'run #' bisect.txt\?x\=13220283200000 | wc -l
168
$ grep -F 'Connection timed out' bisect.txt\?x\=13220283200000 | wc -l
108
$ grep -F 'crashed' bisect.txt\?x\=13220283200000
run #0: crashed: WARNING: ODEBUG bug in netdev_freemem
run #0: crashed: WARNING: ODEBUG bug in netdev_freemem
run #1: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in sys_sendfile64
run #0: crashed: INFO: rcu detected stall in corrupted
run #4: crashed: INFO: rcu detected stall in sys_sendfile64
run #0: crashed: INFO: rcu detected stall in corrupted
run #1: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in ext4_file_write_iter
run #0: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in sendfile64
run #0: crashed: INFO: rcu detected stall in corrupted
run #1: crashed: INFO: rcu detected stall in sendfile64
run #0: crashed: INFO: rcu detected stall in ext4_file_write_iter
run #1: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in corrupted
run #1: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in corrupted
run #3: crashed: INFO: rcu detected stall in corrupted
run #0: crashed: INFO: rcu detected stall in do_iter_write
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: INFO: rcu detected stall in sys_sendfile64 (2)
2019-03-12 4:08 ` Al Viro
2019-03-12 8:00 ` Jani Nikula
2019-03-12 14:29 ` Tetsuo Handa
@ 2019-03-12 17:10 ` Dmitry Vyukov
2 siblings, 0 replies; 5+ messages in thread
From: Dmitry Vyukov @ 2019-03-12 17:10 UTC (permalink / raw)
To: Al Viro
Cc: syzbot, David Airlie, Andrew Morton, Amir Goldstein,
Chris Wilson, Darrick J. Wong, Dave Chinner, DRI, eparis,
Johannes Weiner, Hugh Dickins, intel-gfx, Jan Kara, Jani Nikula,
Joonas Lahtinen, Souptick Joarder, LKML, Linux-MM, Ingo Molnar,
mszeredi
On Tue, Mar 12, 2019 at 5:08 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Mon, Mar 11, 2019 at 08:59:00PM -0700, syzbot wrote:
> > syzbot has bisected this bug to:
> >
> > commit 34e07e42c55aeaa78e93b057a6664e2ecde3fadb
> > Author: Chris Wilson <chris@chris-wilson.co.uk>
> > Date: Thu Feb 8 10:54:48 2018 +0000
> >
> > drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early
> >
> > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13220283200000
> > start commit: 34e07e42 drm/i915: Add missing kerneldoc for 'ent' in i915..
> > git tree: upstream
> > final crash: https://syzkaller.appspot.com/x/report.txt?x=10a20283200000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=17220283200000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=abc3dc9b7a900258
> > dashboard link: https://syzkaller.appspot.com/bug?extid=1505c80c74256c6118a5
> > userspace arch: amd64
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12c4dc28c00000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15df4108c00000
> >
> > Reported-by: syzbot+1505c80c74256c6118a5@syzkaller.appspotmail.com
> > Fixes: 34e07e42 ("drm/i915: Add missing kerneldoc for 'ent' in
> > i915_driver_init_early")
>
> Umm... Might be a good idea to add some plausibility filters - it is,
> in theory, possible that adding a line in a comment changes behaviour
> (without compiler bugs, even - playing with __LINE__ is all it would
> take), but the odds that it's _not_ a false positive are very low.
Thanks for pointing this out.
I've started collecting all such cases, so that we are able to draw
broader conclusions later:
https://github.com/google/syzkaller/issues/1051
added for this one:
=========
A mix of problems: unrelated bug triggered by the same repro
("WARNING: ODEBUG bug in netdev_freemem"); lots of infrastructure
failures ("failed to copy test binary to VM"); also the original
failure seems to be flaky. All this contributed to pointing to a
random commit.
Al Viro points out that the commit only touches comments, so we could
mark the end result as suspicious.
=========
The infrastructure problems is definitely something we need to fix
("failed to copy test binary to VM") (currently the machine hangs
periodically with lots of time consumed by dmcrypt, but I don't know
if it's related or not yet).
Re the comment-only changes, I would like to see more cases where it
would help before we start creating new universes for this. We could
parse sources with clang to understand that a change was comment-only,
but I guess kernel is mostly broken with clang throughout history....
^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-03-12 3:59 ` INFO: rcu detected stall in sys_sendfile64 (2) syzbot
2019-03-12 4:08 ` Al Viro
2019-03-12 8:00 ` Jani Nikula
2019-03-12 14:29 ` Tetsuo Handa
2019-03-12 17:10 ` Dmitry Vyukov
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