Hello,
I am hitting the following use-after-free while running syzkaller fuzzer on commit 8e0f93cda48ed054e1216bab5c60017e1a5fc1e8
================================================================== BUG: KASAN: use-after-free in __list_del_entry+0x1d3/0x1e0 at addr ffff88002ebf6e20 Read of size 8 by task syz-executor/7684 ============================================================================= BUG kmalloc-256 (Not tainted): kasan: bad access detected -----------------------------------------------------------------------------
INFO: Allocated in snd_timer_instance_new+0x52/0x3a0 age=5 cpu=0 pid=7693 [< none >] ___slab_alloc+0x578/0x5d0 mm/slub.c:2464 [< none >] __slab_alloc+0x66/0xc0 mm/slub.c:2493 [< inline >] slab_alloc_node mm/slub.c:2556 [< inline >] slab_alloc mm/slub.c:2598 [< none >] kmem_cache_alloc_trace+0x242/0x3b0 mm/slub.c:2615 [< inline >] kmalloc include/linux/slab.h:463 [< inline >] kzalloc include/linux/slab.h:607 [< none >] snd_timer_instance_new+0x52/0x3a0 sound/core/timer.c:106 [< none >] snd_timer_open+0x522/0xd20 sound/core/timer.c:289 [< inline >] snd_timer_user_tselect sound/core/timer.c:1612 [< inline >] __snd_timer_user_ioctl sound/core/timer.c:1888 [< none >] snd_timer_user_ioctl+0x8f4/0x2490 sound/core/timer.c:1918 [< inline >] vfs_ioctl fs/ioctl.c:43 [< none >] do_vfs_ioctl+0x18c/0xfb0 fs/ioctl.c:674 [< inline >] SYSC_ioctl fs/ioctl.c:689 [< none >] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680 [< none >] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185
INFO: Freed in snd_timer_close+0x3ee/0x750 age=9 cpu=0 pid=7693 [< none >] __slab_free+0x1fc/0x320 mm/slub.c:2674 [< inline >] slab_free mm/slub.c:2829 [< none >] kfree+0x2f5/0x370 mm/slub.c:3660 [< none >] snd_timer_close+0x3ee/0x750 sound/core/timer.c:375 [< inline >] snd_timer_user_tselect sound/core/timer.c:1602 [< inline >] __snd_timer_user_ioctl sound/core/timer.c:1888 [< none >] snd_timer_user_ioctl+0x7cd/0x2490 sound/core/timer.c:1918 [< inline >] vfs_ioctl fs/ioctl.c:43 [< none >] do_vfs_ioctl+0x18c/0xfb0 fs/ioctl.c:674 [< inline >] SYSC_ioctl fs/ioctl.c:689 [< none >] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680 [< none >] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185
INFO: Slab 0xffffea0000bafd00 objects=22 used=11 fp=0xffff88002ebf6d80 flags=0x1fffc0000004080 INFO: Object 0xffff88002ebf6d80 @offset=11648 fp=0xffff88002ebf5110 CPU: 3 PID: 7684 Comm: syz-executor Tainted: G B 4.5.0-rc7+ #337 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 ffffffff87b7d480 ffff88006d707bb0 ffffffff82c2125f ffffffff00bafd00 fffffbfff0f6fa90 ffff88003e807000 ffff88002ebf6d80 ffff88002ebf4000 ffffea0000bafd00 ffff88002ebf6e18 ffff88006d707be0 ffffffff8176dcc4
Call Trace: [<ffffffff81777e4e>] __asan_report_load8_noabort+0x3e/0x40 mm/kasan/report.c:295 [<ffffffff82c88f63>] __list_del_entry+0x1d3/0x1e0 lib/list_debug.c:48 [< inline >] list_del_init include/linux/list.h:145 [<ffffffff852942f9>] snd_timer_interrupt+0x5b9/0xc80 sound/core/timer.c:791 [<ffffffff8529acc9>] snd_hrtimer_callback+0x169/0x230 sound/core/hrtimer.c:54 [< inline >] __run_hrtimer kernel/time/hrtimer.c:1248 [<ffffffff814c3911>] __hrtimer_run_queues+0x331/0xe90 kernel/time/hrtimer.c:1312 [<ffffffff814c62e2>] hrtimer_interrupt+0x182/0x430 kernel/time/hrtimer.c:1346 [<ffffffff81255ec2>] local_apic_timer_interrupt+0x72/0xe0 arch/x86/kernel/apic/apic.c:907 [<ffffffff812593e9>] smp_apic_timer_interrupt+0x79/0xa0 arch/x86/kernel/apic/apic.c:931 [<ffffffff866d256c>] apic_timer_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:520 [< inline >] spin_unlock_irqrestore include/linux/spinlock.h:362 [<ffffffff8177369e>] __slab_free+0x1ae/0x320 mm/slub.c:2681 [< inline >] slab_free mm/slub.c:2829 [<ffffffff81773ed8>] kmem_cache_free+0x318/0x440 mm/slub.c:2838 [<ffffffff81704cb8>] ptlock_free+0x38/0x50 mm/memory.c:3912 [< inline >] pgtable_pmd_page_dtor include/linux/mm.h:1702 [<ffffffff812951ca>] ___pmd_free_tlb+0xaa/0x110 arch/x86/mm/pgtable.c:74 [< inline >] __pmd_free_tlb ./arch/x86/include/asm/pgalloc.h:106 [< inline >] free_pmd_range mm/memory.c:432 [< inline >] free_pud_range mm/memory.c:450 [<ffffffff816f4dc3>] free_pgd_range+0x973/0xbe0 mm/memory.c:526 [<ffffffff816f52f5>] free_pgtables+0x2c5/0x3b0 mm/memory.c:558 [<ffffffff817137c3>] exit_mmap+0x233/0x410 mm/mmap.c:2868 [<ffffffff813543f5>] mmput+0x95/0x230 kernel/fork.c:706 [< inline >] exit_mm kernel/exit.c:436 [<ffffffff81366eb2>] do_exit+0x7b2/0x2d00 kernel/exit.c:735 [<ffffffff81369578>] do_group_exit+0x108/0x330 kernel/exit.c:878 [<ffffffff8138cf14>] get_signal+0x634/0x15e0 kernel/signal.c:2307 [<ffffffff811a7db3>] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712 [<ffffffff81006685>] exit_to_usermode_loop+0x1a5/0x210 arch/x86/entry/common.c:247 [< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282 [<ffffffff8100866a>] syscall_return_slowpath+0x2ba/0x340 arch/x86/entry/common.c:344 [<ffffffff866d18e2>] int_ret_from_sys_call+0x25/0x9f arch/x86/entry/entry_64.S:281
================================================================== kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Modules linked in: CPU: 3 PID: 7684 Comm: syz-executor Tainted: G B 4.5.0-rc7+ #337 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff880061062f80 ti: ffff88005ee10000 task.ti: ffff88005ee10000 RIP: 0010:[<ffffffff82c88e16>] [<ffffffff82c88e16>] __list_del_entry+0x86/0x1e0 RSP: 0018:ffff88006d707cd0 EFLAGS: 00010046 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88002ebf6e18 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffff88006d707cf0 R08: ffffffff89cbcf00 R09: 0000000000000000 R10: ffffed000dae0f8c R11: 0000000000000000 R12: ffff88005ee0d120 R13: ffff8800670a2298 R14: ffff88005ee0d110 R15: ffff88002ebf6e18 FS: 0000000000000000(0000) GS:ffff88006d700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00000000006e0000 CR3: 0000000007ae9000 CR4: 00000000000006e0 Stack: ffff88006d707cf0 ffff88002ebf6e18 dffffc0000000000 ffff88005ee0d120 ffff88006d707db0 ffffffff852942f9 ffff8800670a2368 0000000000000082 dffffc0000000000 ffff8800670a234c ffffffff87b7d480 ffffed000ce1446d Call Trace: <IRQ> [< inline >] list_del_init include/linux/list.h:145 [<ffffffff852942f9>] snd_timer_interrupt+0x5b9/0xc80 sound/core/timer.c:791 [<ffffffff8529acc9>] snd_hrtimer_callback+0x169/0x230 sound/core/hrtimer.c:54 [< inline >] __run_hrtimer kernel/time/hrtimer.c:1248 [<ffffffff814c3911>] __hrtimer_run_queues+0x331/0xe90 kernel/time/hrtimer.c:1312 [<ffffffff814c62e2>] hrtimer_interrupt+0x182/0x430 kernel/time/hrtimer.c:1346 [<ffffffff81255ec2>] local_apic_timer_interrupt+0x72/0xe0 arch/x86/kernel/apic/apic.c:907 [<ffffffff812593e9>] smp_apic_timer_interrupt+0x79/0xa0 arch/x86/kernel/apic/apic.c:931 [<ffffffff866d256c>] apic_timer_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:520 <EOI> [< inline >] spin_unlock_irqrestore include/linux/spinlock.h:362 [<ffffffff8177369e>] __slab_free+0x1ae/0x320 mm/slub.c:2681 [< inline >] slab_free mm/slub.c:2829 [<ffffffff81773ed8>] kmem_cache_free+0x318/0x440 mm/slub.c:2838 [<ffffffff81704cb8>] ptlock_free+0x38/0x50 mm/memory.c:3912 [< inline >] pgtable_pmd_page_dtor include/linux/mm.h:1702 [<ffffffff812951ca>] ___pmd_free_tlb+0xaa/0x110 arch/x86/mm/pgtable.c:74 [< inline >] __pmd_free_tlb ./arch/x86/include/asm/pgalloc.h:106 [< inline >] free_pmd_range mm/memory.c:432 [< inline >] free_pud_range mm/memory.c:450 [<ffffffff816f4dc3>] free_pgd_range+0x973/0xbe0 mm/memory.c:526 [<ffffffff816f52f5>] free_pgtables+0x2c5/0x3b0 mm/memory.c:558 [<ffffffff817137c3>] exit_mmap+0x233/0x410 mm/mmap.c:2868 [<ffffffff813543f5>] mmput+0x95/0x230 kernel/fork.c:706 [< inline >] exit_mm kernel/exit.c:436 [<ffffffff81366eb2>] do_exit+0x7b2/0x2d00 kernel/exit.c:735 [<ffffffff81369578>] do_group_exit+0x108/0x330 kernel/exit.c:878 [<ffffffff8138cf14>] get_signal+0x634/0x15e0 kernel/signal.c:2307 [<ffffffff811a7db3>] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712 [<ffffffff81006685>] exit_to_usermode_loop+0x1a5/0x210 arch/x86/entry/common.c:247 [< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282 [<ffffffff8100866a>] syscall_return_slowpath+0x2ba/0x340 arch/x86/entry/common.c:344 [<ffffffff866d18e2>] int_ret_from_sys_call+0x25/0x9f arch/x86/entry/entry_64.S:281 Code: c0 0f 84 91 00 00 00 48 b8 00 02 00 00 00 00 ad de 48 39 c3 0f 84 9f 00 00 00 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 f6 00 00 00 4c 8b 23 4c 39 e1 0f 85 95 00 00 RIP [<ffffffff82c88e16>] __list_del_entry+0x86/0x1e0 lib/list_debug.c:57 RSP <ffff88006d707cd0> ---[ end trace fd16e1eaa1720656 ]--- Kernel panic - not syncing: Fatal exception in interrupt Shutting down cpus with NMI Kernel Offset: disabled ---[ end Kernel panic - not syncing: Fatal exception in interrupt
It is not easily reproducible. I've hit several times while running fuzzer for a week. Here is one of the logs for the record: https://gist.githubusercontent.com/dvyukov/c84798ee55721563ecb537c4d51dc9f5/...