Re: [linux-next:master] [mempool] 022e94e2c3: BUG:KASAN:double-free_in_mempool_free

[Christoph Hellwig]

Maybe I'm misunderstanding the trace, but AFAICS this comes from
the KASAN kunit test that injects a double free, and the trace
shows that KASAN indeed detected the double free and everything is
fine. Or did I misunderstand the report?

On Thu, Nov 20, 2025 at 01:57:20PM +0800, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed "BUG:KASAN:double-free_in_mempool_free" on:
>
> commit: 022e94e2c304505973d00dedca4b1432c231fbf6 ("mempool: add mempool_{alloc,free}_bulk")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
>
> [test failed on linux-next/master 187dac290bfd0741b9d7d5490af825c33fd9baa4]
>
> in testcase: kunit
> version:
> with following parameters:
>
> group: group-03
>
>
>
> config: x86_64-rhel-9.4-kunit
> compiler: gcc-14
> test machine: 8 threads 1 sockets Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz (Haswell) with 16G memory
>
> (please refer to attached dmesg/kmsg for entire log/backtrace)
>
>
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <olive...@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202511201309...@intel.com
>
>
> kern :err : [ 152.903458] [ T4181] ==================================================================
> kern :err : [ 152.916375] [ T4181] BUG: KASAN: double-free in mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :err : [ 152.922918] [ T4181] Free of addr ffff88812a92b800 by task kunit_try_catch/4181
>
> kern :err : [ 152.932343] [ T4181] CPU: 2 UID: 0 PID: 4181 Comm: kunit_try_catch Tainted: G S B N 6.18.0-rc3-00007-g022e94e2c304 #1 PREEMPT(voluntary)
> kern :err : [ 152.932348] [ T4181] Tainted: [S]=CPU_OUT_OF_SPEC, [B]=BAD_PAGE, [N]=TEST
> kern :err : [ 152.932350] [ T4181] Hardware name: Dell Inc. OptiPlex 9020/0DNKMN, BIOS A05 12/05/2013
> kern :err : [ 152.932351] [ T4181] Call Trace:
> kern :err : [ 152.932353] [ T4181] <TASK>
> kern :err : [ 152.932354] [ T4181] dump_stack_lvl (lib/dump_stack.c:122)
> kern :err : [ 152.932358] [ T4181] print_address_description+0x88/0x320
> kern :err : [ 152.932362] [ T4181] print_report (mm/kasan/report.c:483)
> kern :err : [ 152.932365] [ T4181] ? mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :err : [ 152.932367] [ T4181] kasan_report_invalid_free (mm/kasan/report.c:563)
> kern :err : [ 152.932371] [ T4181] ? mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :err : [ 152.932374] [ T4181] ? mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :err : [ 152.932376] [ T4181] ? mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :err : [ 152.932378] [ T4181] check_slab_allocation (mm/kasan/common.c:230)
> kern :err : [ 152.932381] [ T4181] __kasan_mempool_poison_object (mm/kasan/common.c:542 (discriminator 1))
> kern :err : [ 152.932384] [ T4181] mempool_free_bulk (mm/mempool.c:137 mm/mempool.c:160 mm/mempool.c:653)
> kern :err : [ 152.932387] [ T4181] ? mempool_init_node (mm/mempool.c:140 mm/mempool.c:160 mm/mempool.c:245)
> kern :err : [ 152.932389] [ T4181] ? _raw_spin_lock_irqsave (arch/x86/include/asm/atomic.h:107 (discriminator 4) include/linux/atomic/atomic-arch-fallback.h:2170 (discriminator 4) include/linux/atomic/atomic-instrumented.h:1302 (discriminator 4) include/asm-generic/qspinlock.h:111 (discriminator 4) include/linux/spinlock.h:187 (discriminator 4) include/linux/spinlock_api_smp.h:111 (discriminator 4) kernel/locking/spinlock.c:162 (discriminator 4))
> kern :err : [ 152.932393] [ T4181] mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :err : [ 152.932395] [ T4181] ? __pfx_mempool_free (mm/mempool.c:686)
> kern :err : [ 152.932398] [ T4181] ? kasan_save_track (mm/kasan/common.c:69 (discriminator 1) mm/kasan/common.c:78 (discriminator 1))
> kern :err : [ 152.932400] [ T4181] ? remove_element (mm/mempool.c:172)
> kern :err : [ 152.932414] [ T4181] mempool_double_free_helper (mm/kasan/kasan_test_c.c:1444 (discriminator 17)) kasan_test
> kern :err : [ 152.932423] [ T4181] ? __pfx_mempool_double_free_helper (mm/kasan/kasan_test_c.c:1436) kasan_test
> kern :err : [ 152.932440] [ T4181] ? sched_clock (arch/x86/include/asm/preempt.h:95 arch/x86/kernel/tsc.c:289)
> kern :err : [ 152.932442] [ T4181] ? __update_idle_core (kernel/sched/sched.h:1340 kernel/sched/fair.c:7584)
> kern :err : [ 152.932445] [ T4181] mempool_kmalloc_double_free (mm/kasan/kasan_test_c.c:1457) kasan_test
> kern :err : [ 152.932453] [ T4181] ? __pfx_mempool_kmalloc_double_free (mm/kasan/kasan_test_c.c:1448) kasan_test
> kern :err : [ 152.932461] [ T4181] ? __switch_to (arch/x86/include/asm/cpufeature.h:101 arch/x86/kernel/process_64.c:378 arch/x86/kernel/process_64.c:666)
> kern :err : [ 152.932463] [ T4181] ? __pfx_mempool_kmalloc (mm/mempool.c:715)
> kern :err : [ 152.932466] [ T4181] ? __pfx_mempool_kfree (mm/mempool.c:722)
> kern :err : [ 152.932468] [ T4181] ? __pfx_read_tsc (arch/x86/include/asm/tsc.h:57 arch/x86/kernel/tsc.c:1134)
> kern :err : [ 152.932471] [ T4181] ? ktime_get_ts64 (kernel/time/timekeeping.c:387 kernel/time/timekeeping.c:404 kernel/time/timekeeping.c:967)
> kern :err : [ 152.932474] [ T4181] ? __pfx___schedule (kernel/sched/core.c:6785)
> kern :err : [ 152.932477] [ T4181] kunit_try_run_case (lib/kunit/test.c:450 lib/kunit/test.c:493)
> kern :err : [ 152.932480] [ T4181] ? __pfx_kunit_try_run_case (lib/kunit/test.c:480)
> kern :err : [ 152.932483] [ T4181] ? _raw_spin_lock_irqsave (arch/x86/include/asm/atomic.h:107 (discriminator 4) include/linux/atomic/atomic-arch-fallback.h:2170 (discriminator 4) include/linux/atomic/atomic-instrumented.h:1302 (discriminator 4) include/asm-generic/qspinlock.h:111 (discriminator 4) include/linux/spinlock.h:187 (discriminator 4) include/linux/spinlock_api_smp.h:111 (discriminator 4) kernel/locking/spinlock.c:162 (discriminator 4))
> kern :err : [ 152.932486] [ T4181] ? __pfx__raw_spin_lock_irqsave (kernel/locking/spinlock.c:161)
> kern :err : [ 152.932489] [ T4181] ? __pfx__raw_spin_lock_irqsave (kernel/locking/spinlock.c:161)
> kern :err : [ 152.932492] [ T4181] ? __pfx_kunit_try_run_case (lib/kunit/test.c:480)
> kern :err : [ 152.932494] [ T4181] ? __pfx_kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:26)
> kern :err : [ 152.932498] [ T4181] kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:31)
> kern :err : [ 152.932501] [ T4181] kthread (kernel/kthread.c:463)
> kern :err : [ 152.932503] [ T4181] ? __pfx_kthread (kernel/kthread.c:412)
> kern :err : [ 152.932505] [ T4181] ? __pfx__raw_spin_lock_irq (kernel/locking/spinlock.c:169)
> kern :err : [ 152.932509] [ T4181] ? __pfx_kthread (kernel/kthread.c:412)
> kern :err : [ 152.932511] [ T4181] ? __pfx_kthread (kernel/kthread.c:412)
> kern :err : [ 152.932513] [ T4181] ret_from_fork (arch/x86/kernel/process.c:164)
> kern :err : [ 152.932516] [ T4181] ? __pfx_kthread (kernel/kthread.c:412)
> kern :err : [ 152.932518] [ T4181] ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
> kern :err : [ 152.932522] [ T4181] </TASK>
>
> kern :err : [ 153.201368] [ T4181] Allocated by task 4181:
> kern :warn : [ 153.205558] [ T4181] kasan_save_stack (mm/kasan/common.c:57)
> kern :warn : [ 153.210098] [ T4181] kasan_save_track (mm/kasan/common.c:69 (discriminator 1) mm/kasan/common.c:78 (discriminator 1))
> kern :warn : [ 153.214637] [ T4181] remove_element (mm/mempool.c:172)
> kern :warn : [ 153.219176] [ T4181] mempool_alloc_preallocated (include/linux/spinlock.h:406 mm/mempool.c:409 mm/mempool.c:585)
> kern :warn : [ 153.224582] [ T4181] mempool_double_free_helper (mm/kasan/kasan_test_c.c:1439) kasan_test
> kern :warn : [ 153.231213] [ T4181] mempool_kmalloc_double_free (mm/kasan/kasan_test_c.c:1457) kasan_test
> kern :warn : [ 153.237839] [ T4181] kunit_try_run_case (lib/kunit/test.c:450 lib/kunit/test.c:493)
> kern :warn : [ 153.242727] [ T4181] kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:31)
> kern :warn : [ 153.248830] [ T4181] kthread (kernel/kthread.c:463)
> kern :warn : [ 153.252759] [ T4181] ret_from_fork (arch/x86/kernel/process.c:164)
> kern :warn : [ 153.257211] [ T4181] ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
>
> kern :err : [ 153.264025] [ T4181] Freed by task 4181:
> kern :warn : [ 153.267866] [ T4181] kasan_save_stack (mm/kasan/common.c:57)
> kern :warn : [ 153.272416] [ T4181] kasan_save_track (mm/kasan/common.c:69 (discriminator 1) mm/kasan/common.c:78 (discriminator 1))
> kern :warn : [ 153.276964] [ T4181] __kasan_save_free_info (mm/kasan/generic.c:590 (discriminator 1))
> kern :warn : [ 153.282025] [ T4181] __kasan_mempool_poison_object (mm/kasan/common.c:534)
> kern :warn : [ 153.287868] [ T4181] mempool_free_bulk (mm/mempool.c:137 mm/mempool.c:160 mm/mempool.c:653)
> kern :warn : [ 153.292668] [ T4181] mempool_free (mm/mempool.c:687 (discriminator 1))
> kern :warn : [ 153.296944] [ T4181] mempool_double_free_helper (mm/kasan/kasan_test_c.c:1444 (discriminator 5)) kasan_test
> kern :warn : [ 153.303573] [ T4181] mempool_kmalloc_double_free (mm/kasan/kasan_test_c.c:1457) kasan_test
> kern :warn : [ 153.310203] [ T4181] kunit_try_run_case (lib/kunit/test.c:450 lib/kunit/test.c:493)
> kern :warn : [ 153.315091] [ T4181] kunit_generic_run_threadfn_adapter (lib/kunit/try-catch.c:31)
> kern :warn : [ 153.321198] [ T4181] kthread (kernel/kthread.c:463)
> kern :warn : [ 153.325127] [ T4181] ret_from_fork (arch/x86/kernel/process.c:164)
> kern :warn : [ 153.329576] [ T4181] ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
>
> kern :err : [ 153.336387] [ T4181] The buggy address belongs to the object at ffff88812a92b800
> which belongs to the cache kmalloc-128 of size 128
> kern :err : [ 153.350320] [ T4181] The buggy address is located 0 bytes inside of
> 128-byte region [ffff88812a92b800, ffff88812a92b880)
>
> kern :err : [ 153.365488] [ T4181] The buggy address belongs to the physical page:
> kern :warn : [ 153.371765] [ T4181] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12a92a
> kern :warn : [ 153.380478] [ T4181] head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> kern :warn : [ 153.388842] [ T4181] flags: 0x17ffffc0000040(head|node=0|zone=2|lastcpupid=0x1fffff)
> kern :warn : [ 153.396513] [ T4181] page_type: f5(slab)
> kern :warn : [ 153.400355] [ T4181] raw: 0017ffffc0000040 ffff888100042a00 ffffea00040b9600 0000000000000004
> kern :warn : [ 153.408806] [ T4181] raw: 0000000000000000 0000000080200020 00000000f5000000 0000000000000000
> kern :warn : [ 153.417258] [ T4181] head: 0017ffffc0000040 ffff888100042a00 ffffea00040b9600 0000000000000004
> kern :warn : [ 153.425800] [ T4181] head: 0000000000000000 0000000080200020 00000000f5000000 0000000000000000
> kern :warn : [ 153.434338] [ T4181] head: 0017ffffc0000001 ffffea0004aa4a81 00000000ffffffff 00000000ffffffff
> kern :warn : [ 153.442876] [ T4181] head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
> kern :warn : [ 153.451422] [ T4181] page dumped because: kasan: bad access detected
>
> kern :err : [ 153.459902] [ T4181] Memory state around the buggy address:
> kern :err : [ 153.465395] [ T4181] ffff88812a92b700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> kern :err : [ 153.473335] [ T4181] ffff88812a92b780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> kern :err : [ 153.481266] [ T4181] >ffff88812a92b800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> kern :err : [ 153.489195] [ T4181] ^
> kern :err : [ 153.493121] [ T4181] ffff88812a92b880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> kern :err : [ 153.501051] [ T4181] ffff88812a92b900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> kern :err : [ 153.508980] [ T4181] ==================================================================
> kern :info : [ 153.517054] [ T3993] ok 51 mempool_kmalloc_double_free
> kern :err : [ 153.517141] [ T4183] ==================================================================
>
>
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20251120/202511201309...@intel.com
>
>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
---end quoted text---

[Andrey Ryabinin]

On 11/20/25 8:27 AM, Christoph Hellwig wrote:
> Maybe I'm misunderstanding the trace, but AFAICS this comes from
> the KASAN kunit test that injects a double free, and the trace
> shows that KASAN indeed detected the double free and everything is
> fine. Or did I misunderstand the report?
>

Right, the report comes from the test, so it's expected behavior.

[Vlastimil Babka]

I assume the bot was filtering those, but the changed stacktrace (now
including the new mempool_free_bulk()) now looks new and the filter needs
updating?

[Oliver Sang]

hi, all,

thanks a lot for information! and sorry for false positive.

we will check the kunit test final results in the future.
kernel test robot doesn't have filter so far. we will consider how to improve
this. thanks