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Message-ID: <CA+G9fYt6U4YzYGvYWxDVvUVKNc0pgVYiGafZ5_OSEf=5r1=YYA@mail.gmail.com>
Date: Thu, 11 Apr 2024 20:20:55 +0530
From: Naresh Kamboju <naresh.kamboju@...aro.org>
To: David Gow <davidgow@...gle.com>
Cc: Will Deacon <will@...nel.org>, mic@...ikod.net, keescook@...omium.org,
rmoar@...gle.com, lkft-triage@...ts.linaro.org, kunit-dev@...glegroups.com,
linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...hat.com,
longman@...hat.com, boqun.feng@...il.com, anders.roxell@...aro.org,
dan.carpenter@...aro.org, arnd@...db.de, linux@...ck-us.net,
Linux Kernel Functional Testing <lkft@...aro.org>
Subject: Re: BUG: KASAN: null-ptr-deref in _raw_spin_lock_irq next-20240410
On Thu, 11 Apr 2024 at 20:12, Naresh Kamboju <naresh.kamboju@...aro.org> wrote:
>
> On Thu, 11 Apr 2024 at 09:55, David Gow <davidgow@...gle.com> wrote:
> >
> > On Wed, 10 Apr 2024 at 23:23, Will Deacon <will@...nel.org> wrote:
> > >
> > > On Wed, Apr 10, 2024 at 03:57:10PM +0530, Naresh Kamboju wrote:
> > > > Following kernel crash noticed on Linux next-20240410 tag while running
> > > > kunit testing on qemu-arm64 and qemu-x86_64.
> > > >
> > > > Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> > > >
>
> <trim>
>
> > >
> > > Ok, so 'task_struct->vfork_done' is NULL. Looks like this code was added
> > > recently, so adding Mickaël to cc.
> > >
> >
> > Thanks. This looks like a race condition where the KUnit test kthread
> > can terminate before we wait on it.
> >
> > Mickaël, does this seem like a correct fix to you?
> > ---
> > From: David Gow <davidgow@...gle.com>
> > Date: Thu, 11 Apr 2024 12:07:47 +0800
> > Subject: [PATCH] kunit: Fix race condition in try-catch completion
> >
> > KUnit's try-catch infrastructure now uses vfork_done, which is always
> > set to a valid completion when a kthread is crated, but which is set to
> > NULL once the thread terminates. This creates a race condition, where
> > the kthread exits before we can wait on it.
> >
> > Keep a copy of vfork_done, which is taken before we wake_up_process()
> > and so valid, and wait on that instead.
> >
> > Fixes: 4de2a8e4cca4 ("kunit: Handle test faults")
> > Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
> > Signed-off-by: David Gow <davidgow@...gle.com>
>
> This patch tested on top of Linux next and reported issues fixed.
>
> Tested-by: Linux Kernel Functional Testing <lkft@...aro.org>
>
> > ---
> > lib/kunit/try-catch.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
> > index fa687278ccc9..fc6cd4d7e80f 100644
> > --- a/lib/kunit/try-catch.c
> > +++ b/lib/kunit/try-catch.c
> > @@ -63,6 +63,7 @@ void kunit_try_catch_run(struct kunit_try_catch
> > *try_catch, void *context)
> > {
> > struct kunit *test = try_catch->test;
> > struct task_struct *task_struct;
> > + struct completion *task_done;
> > int exit_code, time_remaining;
> >
> > try_catch->context = context;
> > @@ -75,13 +76,14 @@ void kunit_try_catch_run(struct kunit_try_catch
> > *try_catch, void *context)
> > return;
> > }
> > get_task_struct(task_struct);
> > + task_done = task_struct->vfork_done;
> > wake_up_process(task_struct);
> > /*
> > * As for a vfork(2), task_struct->vfork_done (pointing to the
> > * underlying kthread->exited) can be used to wait for the end of a
> > * kernel thread.
> > */
> > - time_remaining = wait_for_completion_timeout(task_struct->vfork_done,
> > + time_remaining = wait_for_completion_timeout(task_done,
> > kunit_test_timeout());
> > if (time_remaining == 0) {
> > try_catch->try_result = -ETIMEDOUT;
> > --
I use to notice kernel panic while running kunit tests
now I have noticed this
Unable to handle kernel paging request at virtual address
KASAN: null-ptr-deref in range
pc : kunit_test_null_dereference (lib/kunit/kunit-test.c:119)
lr : kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:31)
The kunit tests run to completion and the system is stable.
Kernel did not panic.
kunit test log:
------
<6>[ 76.784878] # Subtest: kunit_fault
<6>[ 76.785527] # module: kunit_test
<6>[ 76.785785] 1..1
<1>[ 76.794318] Unable to handle kernel paging request at virtual
address dfff800000000000
<1>[ 76.796137] KASAN: null-ptr-deref in range
[0x0000000000000000-0x0000000000000007]
<1>[ 76.796970] Mem abort info:
<1>[ 76.797685] ESR = 0x0000000096000005
<1>[ 76.798868] EC = 0x25: DABT (current EL), IL = 32 bits
<1>[ 76.800355] SET = 0, FnV = 0
<1>[ 76.800893] EA = 0, S1PTW = 0
<1>[ 76.801715] FSC = 0x05: level 1 translation fault
<1>[ 76.802654] Data abort info:
<1>[ 76.803713] ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
<1>[ 76.804362] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
<1>[ 76.805278] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
<1>[ 76.806302] [dfff800000000000] address between user and kernel
address ranges
<0>[ 76.808597] Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
<4>[ 76.809876] Modules linked in:
<4>[ 76.812055] CPU: 1 PID: 567 Comm: kunit_try_catch Tainted: G
B N 6.9.0-rc3-next-20240410 #1
<4>[ 76.812987] Hardware name: linux,dummy-virt (DT)
<4>[ 76.814123] pstate: 12400009 (nzcV daif +PAN -UAO +TCO -DIT
-SSBS BTYPE=--)
<4>[ 76.814947] pc : kunit_test_null_dereference (lib/kunit/kunit-test.c:119)
<4>[ 76.815862] lr : kunit_generic_run_threadfn_adapter
(lib/kunit/try-catch.c:31)
<4>[ 76.816765] sp : ffff800083137dc0
<4>[ 76.817473] x29: ffff800083137e20 x28: 0000000000000000 x27:
0000000000000000
<4>[ 76.818684] x26: 0000000000000000 x25: 0000000000000000 x24:
fff00000c1b30c00
<4>[ 76.819798] x23: ffffa76fb372e348 x22: ffffa76fb3736550 x21:
fff00000c1b30c08
<4>[ 76.820900] x20: 1ffff00010626fb8 x19: ffff8000800879f0 x18:
0000000000000068
<4>[ 76.822008] x17: 0000000000000000 x16: fff00000da132180 x15:
ffffa76fb36f3b04
<4>[ 76.823125] x14: ffffa76fb2e3cc28 x13: 1ffe0000181547e4 x12:
fffd80001832511a
<4>[ 76.824229] x11: 1ffe000018325119 x10: fffd800018325119 x9 :
ffffa76fb372e3d0
<4>[ 76.825409] x8 : ffff800083137cb8 x7 : 0000000000000000 x6 :
0000000041b58ab3
<4>[ 76.826532] x5 : ffff700010626fb8 x4 : 00000000f1f1f1f1 x3 :
0000000000000003
<4>[ 76.827653] x2 : dfff800000000000 x1 : fff00000c1928000 x0 :
ffff8000800879f0
<4>[ 76.828829] Call trace:
<4>[ 76.829410] kunit_test_null_dereference (lib/kunit/kunit-test.c:119)
<4>[ 76.830294] kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:31)
<4>[ 76.831168] kthread (kernel/kthread.c:389)
<4>[ 76.831870] ret_from_fork (arch/arm64/kernel/entry.S:861)
<0>[ 76.833252] Code: b90004a3 d5384101 52800063 aa0003f3 (39c00042)
All code
========
0: b90004a3 str w3, [x5, #4]
4: d5384101 mrs x1, sp_el0
8: 52800063 mov w3, #0x3 // #3
c: aa0003f3 mov x19, x0
10:* 39c00042 ldrsb w2, [x2] <-- trapping instruction
Code starting with the faulting instruction
===========================================
0: 39c00042 ldrsb w2, [x2]
<4>[ 76.834489] ---[ end trace 0000000000000000 ]---
Links:
- https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/2exQ84OHGOdSUQMBfFMxJoo8tAo
--
Linaro LKFT
https://lkft.linaro.org
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