Re: BUG: KASAN: null-ptr-deref in _raw_spin_lock_irq next-20240410

[Will Deacon]

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@xxxxxxxxxx>
> 
> Crash log on qemu-arm64:
> ----------------
> <3>[ 30.465716] BUG: KASAN: null-ptr-deref in _raw_spin_lock_irq (include/linux/instrumented.h:96 include/linux/atomic/atomic-instrumented.h:1301 include/asm-generic/qspinlock.h:111 include/linux/spinlock.h:187 include/linux/spinlock_api_smp.h:120 kernel/locking/spinlock.c:170) 
> <3>[   30.467097] Write of size 4 at addr 0000000000000008 by task swapper/0/1
> <3>[   30.468059]
> <3>[   30.468393] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G    B            N 6.9.0-rc3-next-20240410 #1
> <3>[   30.469209] Hardware name: linux,dummy-virt (DT)
> <3>[   30.469645] Call trace:
> <3>[ 30.469919] dump_backtrace (arch/arm64/kernel/stacktrace.c:319) 
> <3>[ 30.471622] show_stack (arch/arm64/kernel/stacktrace.c:326) 
> <3>[ 30.472124] dump_stack_lvl (lib/dump_stack.c:117) 
> <3>[ 30.472947] print_report (mm/kasan/report.c:493) 
> <3>[ 30.473755] kasan_report (mm/kasan/report.c:603) 
> <3>[ 30.474524] kasan_check_range (mm/kasan/generic.c:175 mm/kasan/generic.c:189) 
> <3>[ 30.475094] __kasan_check_write (mm/kasan/shadow.c:38) 
> <3>[ 30.475683] _raw_spin_lock_irq (include/linux/instrumented.h:96 include/linux/atomic/atomic-instrumented.h:1301 include/asm-generic/qspinlock.h:111 include/linux/spinlock.h:187 include/linux/spinlock_api_smp.h:120 kernel/locking/spinlock.c:170) 
> <3>[ 30.476257] wait_for_completion_timeout (kernel/sched/completion.c:84 kernel/sched/completion.c:116 kernel/sched/completion.c:127 kernel/sched/completion.c:167) 
> <3>[ 30.476909] kunit_try_catch_run (lib/kunit/try-catch.c:86) 
> <3>[ 30.477628] kunit_run_case_catch_errors (lib/kunit/test.c:544) 
> <3>[ 30.478311] kunit_run_tests (lib/kunit/test.c:635) 
> <3>[ 30.478865] __kunit_test_suites_init (lib/kunit/test.c:729 (discriminator 1)) 
> <3>[ 30.479482] kunit_run_all_tests (lib/kunit/executor.c:276 lib/kunit/executor.c:392) 
> <3>[ 30.480079] kernel_init_freeable (init/main.c:1578) 
> <3>[ 30.480747] kernel_init (init/main.c:1465) 
> <3>[ 30.481474] ret_from_fork (arch/arm64/kernel/entry.S:861) 
> <3>[   30.482080] ==================================================================
> <1>[   30.484503] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
> <1>[   30.485369] Mem abort info:
> <1>[   30.485923]   ESR = 0x000000009600006b
> <1>[   30.486943]   EC = 0x25: DABT (current EL), IL = 32 bits
> <1>[   30.487540]   SET = 0, FnV = 0
> <1>[   30.488007]   EA = 0, S1PTW = 0
> <1>[   30.488509]   FSC = 0x2b: level -1 translation fault
> <1>[   30.489150] Data abort info:
> <1>[   30.489610]   ISV = 0, ISS = 0x0000006b, ISS2 = 0x00000000
> <1>[   30.490360]   CM = 0, WnR = 1, TnD = 0, TagAccess = 0
> <1>[   30.491057]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> <1>[   30.491822] [0000000000000008] user address but active_mm is swapper
> <0>[   30.493008] Internal error: Oops: 000000009600006b [#1] PREEMPT SMP
> <4>[   30.494105] Modules linked in:
> <4>[   30.496244] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G    B            N 6.9.0-rc3-next-20240410 #1
> <4>[   30.497171] Hardware name: linux,dummy-virt (DT)
> <4>[   30.497905] pstate: 224000c9 (nzCv daIF +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
> <4>[ 30.498895] pc : _raw_spin_lock_irq (arch/arm64/include/asm/atomic_lse.h:271 arch/arm64/include/asm/cmpxchg.h:120 arch/arm64/include/asm/cmpxchg.h:169 include/linux/atomic/atomic-arch-fallback.h:2055 include/linux/atomic/atomic-arch-fallback.h:2173 include/linux/atomic/atomic-instrumented.h:1302 include/asm-generic/qspinlock.h:111 include/linux/spinlock.h:187 include/linux/spinlock_api_smp.h:120 kernel/locking/spinlock.c:170) 
> <4>[ 30.499542] lr : _raw_spin_lock_irq (include/linux/atomic/atomic-arch-fallback.h:2172 (discriminator 1) include/linux/atomic/atomic-instrumented.h:1302 (discriminator 1) include/asm-generic/qspinlock.h:111 (discriminator 1) include/linux/spinlock.h:187 (discriminator 1) include/linux/spinlock_api_smp.h:120 (discriminator 1) kernel/locking/spinlock.c:170 (discriminator 1)) 
> 
> <trim>

It's a shame that you have trimmed the register dump here.

> <4>[   30.511022] Call trace:
> <4>[ 30.511437] _raw_spin_lock_irq (arch/arm64/include/asm/atomic_lse.h:271 arch/arm64/include/asm/cmpxchg.h:120 arch/arm64/include/asm/cmpxchg.h:169 include/linux/atomic/atomic-arch-fallback.h:2055 include/linux/atomic/atomic-arch-fallback.h:2173 include/linux/atomic/atomic-instrumented.h:1302 include/asm-generic/qspinlock.h:111 include/linux/spinlock.h:187 include/linux/spinlock_api_smp.h:120 kernel/locking/spinlock.c:170) 
> <4>[ 30.512013] wait_for_completion_timeout (kernel/sched/completion.c:84 kernel/sched/completion.c:116 kernel/sched/completion.c:127 kernel/sched/completion.c:167) 
> <4>[ 30.512627] kunit_try_catch_run (lib/kunit/try-catch.c:86) 
> <4>[ 30.513188] kunit_run_case_catch_errors (lib/kunit/test.c:544) 
> <4>[ 30.513801] kunit_run_tests (lib/kunit/test.c:635) 

Ok, so 'task_struct->vfork_done' is NULL. Looks like this code was added
recently, so adding Mickaël to cc.

Will

> <4>[ 30.514674] __kunit_test_suites_init (lib/kunit/test.c:729 (discriminator 1)) 
> <4>[ 30.515259] kunit_run_all_tests (lib/kunit/executor.c:276 lib/kunit/executor.c:392) 
> <4>[ 30.515831] kernel_init_freeable (init/main.c:1578) 
> <4>[ 30.516384] kernel_init (init/main.c:1465) 
> <4>[ 30.516900] ret_from_fork (arch/arm64/kernel/entry.S:861) 
> <0>[ 30.518151] Code: 93407c02 d503201f 2a0003e1 52800022 (88e17e62)
> All code
> ========
>    0:	93407c02 	sxtw	x2, w0
>    4:	d503201f 	nop
>    8:	2a0003e1 	mov	w1, w0
>    c:	52800022 	mov	w2, #0x1                   	// #1
>   10:*	88e17e62 	casa	w1, w2, [x19]		<-- trapping instruction
> 
> Code starting with the faulting instruction
> ===========================================
>    0:	88e17e62 	casa	w1, w2, [x19]
> <4>[   30.519501] ---[ end trace 0000000000000000 ]---
> <6>[   30.520317] note: swapper/0[1] exited with irqs disabled
> <6>[   30.521355] note: swapper/0[1] exited with preempt_count 1
> <0>[   30.523129] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> <2>[   30.524397] SMP: stopping secondary CPUs
> <0>[   30.525553] Kernel Offset: 0x25148d400000 from 0xffff800080000000
> <0>[   30.528341] PHYS_OFFSET: 0x40000000
> <0>[   30.529003] CPU features: 0x0,00000006,8f17bd7c,6766773f
> <0>[   30.530313] Memory Limit: none
> <0>[   30.531319] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
> 
> Steps to reproduce:
> ---
> https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/2etdCz631GU6PILJzs8reteba8i/reproducer
> 
> Links:
>  - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20240410/testrun/23381881/suite/log-parser-test/tests/
>  - https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/2etdCz631GU6PILJzs8reteba8i
>  - https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/2etdDjlx3eRFhhK9cy2UsEHAXTr
> 
> --
> Linaro LKFT
> https://lkft.linaro.org