From: Joel Granados <joel.granados@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: kernel test robot <yi1.lai@intel.com>,
oe-lkp@lists.linux.dev, lkp@intel.com,
linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org,
netdev@vger.kernel.org, wireguard@lists.zx2c4.com,
achender@kernel.org
Subject: Re: [linus:master] [sysctl] 8d75c338f0: BUG:KASAN:slab-use-after-free_in_touch_wq_lockdep_map
Date: Mon, 19 Oct 2026 15:30:41 +0200 [thread overview]
Message-ID: <atYW0K3t57puHeLW@hobbes> (raw)
In-Reply-To: <atYB0bm9eEXp8A2g@redhat.com>
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On Mon, Oct 19, 2026 at 01:41:05PM +0200, Oleg Nesterov wrote:
> On 10/19, kernel test robot wrote:
> >
> >
> > Hello,
> >
> > kernel test robot noticed "BUG:KASAN:slab-use-after-free_in_touch_wq_lockdep_map" on:
> >
> > commit: 8d75c338f0bcecaa6c9af67f86c176b67b6acf3e ("sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors CONFIG_SYSCTL") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> I don't think that commit could cause such a problem. Please re-check.
>
> Oleg.
That commit might not be the one that introduces the UAF, but it might
be the one that exposes it?
You have CONFIG_SYSCTL=n & CONFIG_RDS=y & CONFIG_RDS_RDMA=y.
Therefore rds_sysctl_init() returns -ENOMEM and rds_ib_sysctl_init
returns -ENOMEM.
If rds_ib_sysctl_init is called after a failed rds_sysctl_init, then
rds_ib_sysctl_init would call a flush_workqueue on a rds_wq that has
already been freed by the failed rds_sysctl_init. Right?
Please let me know if I missed anything.
Best
>
> > [test failed on linux-next/master b810335a0699d1810683796b0e3ffe8827ddfe6c]
> >
> > in testcase: boot
> >
> > config: x86_64-randconfig-2300-20261014
> > compiler: gcc-14
> > test machine: qemu-system-x86_64 -enable-kvm -cpu Haswell-noTSX,enforce -smp 4 -m 16G
> >
> > (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 <yi1.lai@intel.com>
> > | Closes: https://lore.kernel.org/oe-lkp/202610190310.9737b2e3-lkp@intel.com
> >
> >
> > [ 35.688893][ T1] BUG: KASAN: slab-use-after-free in touch_wq_lockdep_map (workqueue.c:4031 (discriminator 1))
> > [ 35.688893][ T1] Read of size 8 at addr ffff8881259a2968 by task swapper/0/1
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.2.0-rc2-00010-g8d75c338f0bc #1 PREEMPT
> > [ 35.688893][ T1] Call Trace:
> > [ 35.688893][ T1] <TASK>
> > [ 35.688893][ T1] dump_stack_lvl (dump_stack.c:94 dump_stack.c:120)
> > [ 35.688893][ T1] ? touch_wq_lockdep_map (workqueue.c:4031 (discriminator 1))
> > [ 35.688893][ T1] print_address_description+0x51/0x300
> > [ 35.688893][ T1] ? rcu_is_watching (rcu/tree.c:753 (discriminator 3))
> > [ 35.688893][ T1] ? touch_wq_lockdep_map (workqueue.c:4031 (discriminator 1))
> > [ 35.688893][ T1] print_report (kasan/report.c:482)
> > [ 35.688893][ T1] ? kmem_cache_debug_flags (slab.h:503)
> > [ 35.688893][ T1] ? fixup_red_left (slub.c:250)
> > [ 35.688893][ T1] ? touch_wq_lockdep_map (workqueue.c:4031 (discriminator 1))
> > [ 35.688893][ T1] kasan_report (kasan/report.c:595)
> > [ 35.688893][ T1] ? touch_wq_lockdep_map (workqueue.c:4031 (discriminator 1))
> > [ 35.688893][ T1] touch_wq_lockdep_map (workqueue.c:4031 (discriminator 1))
> > [ 35.688893][ T1] __flush_workqueue (workqueue.c:4079)
> > [ 35.688893][ T1] ? xa_load (xarray.c:1621)
> > [ 35.688893][ T1] ? tracer_preempt_on (trace/trace_irqsoff.c:686 (discriminator 1))
> > [ 35.688893][ T1] ? preempt_count_sub (sched/core.c:6019)
> > [ 35.688893][ T1] ? rcu_is_watching (rcu/tree.c:753 (discriminator 3))
> > [ 35.688893][ T1] ? preempt_count_sub (sched/core.c:6019)
> > [ 35.688893][ T1] ? touch_wq_lockdep_map (workqueue.c:4043)
> > [ 35.688893][ T1] ? __up_write (locking/rwsem.c:1422 (discriminator 4))
> > [ 35.688893][ T1] rds_ib_init (rds/ib.c:618)
> > [ 35.688893][ T1] rds_rdma_init (rds/rdma_transport.c:300)
> > [ 35.688893][ T1] ? rds_init (af_rds.c:?)
> > [ 35.688893][ T1] ? __raw_spin_unlock_irqrestore (linux/spinlock_api_smp.h:179 (discriminator 4))
> > [ 35.688893][ T1] ? add_device_randomness (linux/spinlock.h:408 char/random.c:936)
> > [ 35.688893][ T1] ? random_get_entropy (x86/include/asm/timex.h:11)
> > [ 35.688893][ T1] ? sctp_diag_init (diag.c:?)
> > [ 35.688893][ T1] ? rds_init (rds/af_rds.c:977)
> > [ 35.688893][ T1] ? rcu_is_watching (rcu/tree.c:753 (discriminator 3))
> > [ 35.688893][ T1] ? rds_init (af_rds.c:?)
> > [ 35.688893][ T1] do_one_initcall (main.c:1347)
> > [ 35.688893][ T1] ? trace_initcall_finish_cb (main.c:1289 (discriminator 1))
> > [ 35.688893][ T1] ? __kmalloc_noprof (slub.c:5363 slub.c:5387)
> > [ 35.688893][ T1] ? do_initcalls (linux/slab.h:973 linux/slab.h:1290 main.c:1418)
> > [ 35.688893][ T1] do_initcalls (main.c:1409 (discriminator 1) main.c:1425 (discriminator 1))
> > [ 35.688893][ T1] kernel_init_freeable (main.c:1445 main.c:1658)
> > [ 35.688893][ T1] ? rest_init (main.c:717)
> > [ 35.688893][ T1] kernel_init (main.c:1548)
> > [ 35.688893][ T1] ? rest_init (main.c:717)
> > [ 35.688893][ T1] ret_from_fork (x86/kernel/process.c:158)
> > [ 35.688893][ T1] ? exit_thread (x86/kernel/process.c:138)
> > [ 35.688893][ T1] ? __switch_to (x86/kernel/process_64.c:674)
> > [ 35.688893][ T1] ? rest_init (main.c:717)
> > [ 35.688893][ T1] ret_from_fork_asm (x86/entry/entry_64.S:245)
> > [ 35.688893][ T1] </TASK>
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] Allocated by task 1 on cpu 1 at 35.661878s:
> > [ 35.688893][ T1] stack_trace_save (stacktrace.c:122 (discriminator 1))
> > [ 35.688893][ T1] kasan_save_stack (kasan/common.c:57)
> > [ 35.688893][ T1] kasan_save_track (kasan/common.c:78)
> > [ 35.688893][ T1] __kasan_kmalloc (kasan/common.c:415)
> > [ 35.688893][ T1] __kmalloc_noprof (linux/kasan.h:263 slub.c:5362 slub.c:5387)
> > [ 35.688893][ T1] __alloc_workqueue (workqueue.c:5827)
> > [ 35.688893][ T1] alloc_workqueue_va (workqueue.c:5946)
> > [ 35.688893][ T1] alloc_workqueue_noprof (workqueue.c:5962)
> > [ 35.688893][ T1] rds_threads_init (rds/threads.c:259 (discriminator 2))
> > [ 35.688893][ T1] rds_init (rds/af_rds.c:961)
> > [ 35.688893][ T1] do_one_initcall (main.c:1347)
> > [ 35.688893][ T1] do_initcalls (main.c:1409 (discriminator 1) main.c:1425 (discriminator 1))
> > [ 35.688893][ T1] kernel_init_freeable (main.c:1445 main.c:1658)
> > [ 35.688893][ T1] kernel_init (main.c:1548)
> > [ 35.688893][ T1] ret_from_fork (x86/kernel/process.c:158)
> > [ 35.688893][ T1] ret_from_fork_asm (x86/entry/entry_64.S:245)
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] Freed by task 0 on cpu 3 at 35.674112s:
> > [ 35.688893][ T1] stack_trace_save (stacktrace.c:122 (discriminator 1))
> > [ 35.688893][ T1] kasan_save_stack (kasan/common.c:57)
> > [ 35.688893][ T1] kasan_save_track (kasan/common.c:78)
> > [ 35.688893][ T1] kasan_save_free_info (kasan/generic.c:584)
> > [ 35.688893][ T1] __kasan_slab_free (kasan/common.c:285)
> > [ 35.688893][ T1] kfree (linux/kasan.h:235 slub.c:2705 slub.c:6405 slub.c:6720)
> > [ 35.688893][ T1] rcu_do_batch (rcu/tree.c:2645)
> > [ 35.688893][ T1] rcu_core (rcu/tree.c:2897)
> > [ 35.688893][ T1] handle_softirqs (softirq.c:622)
> > [ 35.688893][ T1] __irq_exit_rcu (softirq.c:496 softirq.c:735)
> > [ 35.688893][ T1] irq_exit_rcu (softirq.c:752)
> > [ 35.688893][ T1] sysvec_apic_timer_interrupt (x86/kernel/apic/apic.c:1062 (discriminator 35) x86/kernel/apic/apic.c:1062 (discriminator 35))
> > [ 35.688893][ T1] asm_sysvec_apic_timer_interrupt (x86/include/asm/idtentry.h:546)
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] Last potentially related work creation:
> > [ 35.688893][ T1] stack_trace_save (stacktrace.c:122 (discriminator 1))
> > [ 35.688893][ T1] kasan_save_stack (kasan/common.c:57)
> > [ 35.688893][ T1] kasan_record_aux_stack (kasan/generic.c:556)
> > [ 35.688893][ T1] __call_rcu_common+0xe6/0x480
> > [ 35.688893][ T1] kthread_worker_fn (kthread.c:1025)
> > [ 35.688893][ T1] kthread (kthread.c:436)
> > [ 35.688893][ T1] ret_from_fork (x86/kernel/process.c:158)
> > [ 35.688893][ T1] ret_from_fork_asm (x86/entry/entry_64.S:245)
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] The buggy address belongs to the object at ffff8881259a2800
> > [ 35.688893][ T1] which belongs to the cache kmalloc-1k of size 1024
> > [ 35.688893][ T1] The buggy address belongs to the object at ffff8881259a2800
> > [ 35.688893][ T1] which belongs to the cache kmalloc-1k of size 1024
> > [ 35.688893][ T1] The buggy address belongs to the object at ffff8881259a2800
> > [ 35.688893][ T1] which belongs to the cache kmalloc-1k of size 1024
> > [ 35.688893][ T1] The buggy address is located 360 bytes inside of
> > [ 35.688893][ T1] freed 1024-byte region [ffff8881259a2800, ffff8881259a2c00)
> > [ 35.688893][ T1] The buggy address is located 360 bytes inside of
> > [ 35.688893][ T1] freed 1024-byte region [ffff8881259a2800, ffff8881259a2c00)
> > [ 35.688893][ T1] The buggy address is located 360 bytes inside of
> > [ 35.688893][ T1] freed 1024-byte region [ffff8881259a2800, ffff8881259a2c00)
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] The buggy address belongs to the physical page:
> > [ 35.688893][ T1] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1259a0
> > [ 35.688893][ T1] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> > [ 35.688893][ T1] flags: 0x4000000000000040(head|zone=2)
> > [ 35.688893][ T1] page_type: f5(slab)
> > [ 35.688893][ T1] raw: 4000000000000040 ffff888100042dc0 dead000000000100 dead000000000122
> > [ 35.688893][ T1] raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
> > [ 35.688893][ T1] head: 4000000000000040 ffff888100042dc0 dead000000000100 dead000000000122
> > [ 35.688893][ T1] head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000
> > [ 35.688893][ T1] head: 4000000000000003 ffffea0004966801 00000000ffffffff 00000000ffffffff
> > [ 35.688893][ T1] head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
> > [ 35.688893][ T1] page dumped because: kasan: bad access detected
> > [ 35.688893][ T1]
> > [ 35.688893][ T1] Memory state around the buggy address:
> > [ 35.688893][ T1] ffff8881259a2800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 35.688893][ T1] ffff8881259a2880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 35.688893][ T1] >ffff8881259a2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 35.688893][ T1] ^
> > [ 35.688893][ T1] ffff8881259a2980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 35.688893][ T1] ffff8881259a2a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 35.688893][ T1] ==================================================================
> > [ 35.984299][ T1] Disabling lock debugging due to kernel taint
> > [ 35.987548][ T1] Oops: general protection fault, probably for non-canonical address 0xe0a07c0ec0000008: 0000 [#1] SMP KASAN
> > [ 35.988482][ T1] KASAN: maybe wild-memory-access in range [0x0504007600000040-0x0504007600000047]
> > [ 35.988482][ T1] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Tainted: G B 7.2.0-rc2-00010-g8d75c338f0bc #1 PREEMPT
> > [ 35.988482][ T1] Tainted: [B]=BAD_PAGE
> > [ 35.988482][ T1] RIP: 0010:do_raw_spin_lock (locking/spinlock_debug.c:86 (discriminator 2) locking/spinlock_debug.c:115 (discriminator 2))
> > [ 35.988482][ T1] Code: 3b 58 81 49 8d 14 04 c7 02 f1 f1 f1 f1 c7 42 04 04 f3 f3 f3 65 48 8b 15 f0 53 f7 08 48 89 54 24 60 31 d2 48 89 fa 48 c1 ea 03 <8a> 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 09 84 d2 74 05 e8 39
> > All code
> > ========
> > 0: 3b 58 81 cmp -0x7f(%rax),%ebx
> > 3: 49 8d 14 04 lea (%r12,%rax,1),%rdx
> > 7: c7 02 f1 f1 f1 f1 movl $0xf1f1f1f1,(%rdx)
> > d: c7 42 04 04 f3 f3 f3 movl $0xf3f3f304,0x4(%rdx)
> > 14: 65 48 8b 15 f0 53 f7 mov %gs:0x8f753f0(%rip),%rdx # 0x8f7540c
> > 1b: 08
> > 1c: 48 89 54 24 60 mov %rdx,0x60(%rsp)
> > 21: 31 d2 xor %edx,%edx
> > 23: 48 89 fa mov %rdi,%rdx
> > 26: 48 c1 ea 03 shr $0x3,%rdx
> > 2a:* 8a 14 02 mov (%rdx,%rax,1),%dl <-- trapping instruction
> > 2d: 48 89 f8 mov %rdi,%rax
> > 30: 83 e0 07 and $0x7,%eax
> >
> >
> > The kernel config and materials to reproduce are available at:
> > https://download.01.org/0day-ci/archive/20261019/202610190310.9737b2e3-lkp@intel.com
> >
> >
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
> >
> >
>
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next prev parent reply other threads:[~2026-10-19 13:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-19 1:46 kernel test robot
2026-10-19 11:41 ` Oleg Nesterov
2026-10-19 13:30 ` Joel Granados [this message]
2026-10-19 14:49 ` Oleg Nesterov
2026-10-19 15:35 ` Oleg Nesterov
2026-10-19 19:52 ` Allison Henderson
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