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Date: Wed, 4 Mar 2020 08:59:29 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: syzbot <syzbot+e017e49c39ab484ac87a@...kaller.appspotmail.com>,
Al Viro <viro@...iv.linux.org.uk>, io-uring@...r.kernel.org,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Jens Axboe <axboe@...nel.dk>
Cc: Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
Thomas Gleixner <tglx@...utronix.de>, tony.luck@...el.com,
"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: KASAN: use-after-free Read in percpu_ref_switch_to_atomic_rcu
On Fri, Feb 7, 2020 at 9:14 AM syzbot
<syzbot+e017e49c39ab484ac87a@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 4c7d00cc Merge tag 'pwm/for-5.6-rc1' of git://git.kernel.o..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12fec785e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=e162021ddededa72
> dashboard link: https://syzkaller.appspot.com/bug?extid=e017e49c39ab484ac87a
> compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+e017e49c39ab484ac87a@...kaller.appspotmail.com
+io_uring maintainers
Here is a repro:
https://gist.githubusercontent.com/dvyukov/6b340beab6483a036f4186e7378882ce/raw/cd1922185516453c201df8eded1d4b006a6d6a3a/gistfile1.txt
> ==================================================================
> BUG: KASAN: use-after-free in percpu_ref_call_confirm_rcu lib/percpu-refcount.c:126 [inline]
> BUG: KASAN: use-after-free in percpu_ref_switch_to_atomic_rcu+0x3f7/0x400 lib/percpu-refcount.c:165
> Read of size 1 at addr ffff8880a8d91830 by task swapper/0/0
>
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.5.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <IRQ>
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x1fb/0x318 lib/dump_stack.c:118
> print_address_description+0x74/0x5c0 mm/kasan/report.c:374
> __kasan_report+0x149/0x1c0 mm/kasan/report.c:506
> kasan_report+0x26/0x50 mm/kasan/common.c:641
> __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132
> percpu_ref_call_confirm_rcu lib/percpu-refcount.c:126 [inline]
> percpu_ref_switch_to_atomic_rcu+0x3f7/0x400 lib/percpu-refcount.c:165
> rcu_do_batch kernel/rcu/tree.c:2186 [inline]
> rcu_core+0x81b/0x10c0 kernel/rcu/tree.c:2410
> rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2419
> __do_softirq+0x283/0x7bd kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:373 [inline]
> irq_exit+0x227/0x230 kernel/softirq.c:413
> exiting_irq arch/x86/include/asm/apic.h:536 [inline]
> smp_apic_timer_interrupt+0x113/0x280 arch/x86/kernel/apic/apic.c:1137
> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
> </IRQ>
> RIP: 0010:native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:61
> Code: 89 d9 80 e1 07 80 c1 03 38 c1 7c ba 48 89 df e8 e4 5f 9d f9 eb b0 cc cc 55 48 89 e5 e9 07 00 00 00 0f 00 2d 62 17 4c 00 fb f4 <5d> c3 66 90 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 e9 07 00 00
> RSP: 0018:ffffffff89207db8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
> RAX: 1ffffffff1255a25 RBX: ffffffff89275b00 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: ffffffff812c06aa RDI: ffffffff89276344
> RBP: ffffffff89207db8 R08: ffffffff89276358 R09: fffffbfff124eb61
> R10: fffffbfff124eb61 R11: 0000000000000000 R12: 1ffffffff124eb60
> R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffffffff1255a23
> arch_safe_halt arch/x86/include/asm/paravirt.h:144 [inline]
> default_idle+0x50/0x70 arch/x86/kernel/process.c:695
> arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:686
> default_idle_call+0x59/0xa0 kernel/sched/idle.c:94
> cpuidle_idle_call kernel/sched/idle.c:154 [inline]
> do_idle+0x1ec/0x630 kernel/sched/idle.c:269
> cpu_startup_entry+0x25/0x30 kernel/sched/idle.c:361
> rest_init+0x29d/0x2b0 init/main.c:450
> arch_call_rest_init+0xe/0x10
> start_kernel+0x676/0x777 init/main.c:784
> x86_64_start_reservations+0x18/0x2e arch/x86/kernel/head64.c:490
> x86_64_start_kernel+0x7a/0x7d arch/x86/kernel/head64.c:471
> secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242
>
> Allocated by task 25166:
> save_stack mm/kasan/common.c:72 [inline]
> set_track mm/kasan/common.c:80 [inline]
> __kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:515
> kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
> kmem_cache_alloc_trace+0x221/0x2f0 mm/slab.c:3551
> kmalloc include/linux/slab.h:555 [inline]
> kzalloc include/linux/slab.h:669 [inline]
> io_sqe_files_register fs/io_uring.c:5528 [inline]
> __io_uring_register fs/io_uring.c:6875 [inline]
> __do_sys_io_uring_register fs/io_uring.c:6955 [inline]
> __se_sys_io_uring_register+0x1df4/0x3260 fs/io_uring.c:6937
> __x64_sys_io_uring_register+0x9b/0xb0 fs/io_uring.c:6937
> do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 25160:
> save_stack mm/kasan/common.c:72 [inline]
> set_track mm/kasan/common.c:80 [inline]
> kasan_set_free_info mm/kasan/common.c:337 [inline]
> __kasan_slab_free+0x12e/0x1e0 mm/kasan/common.c:476
> kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
> __cache_free mm/slab.c:3426 [inline]
> kfree+0x10d/0x220 mm/slab.c:3757
> io_sqe_files_unregister+0x238/0x2b0 fs/io_uring.c:5250
> io_ring_ctx_free fs/io_uring.c:6229 [inline]
> io_ring_ctx_wait_and_kill+0x343d/0x3b00 fs/io_uring.c:6310
> io_uring_release+0x5d/0x70 fs/io_uring.c:6318
> __fput+0x2e4/0x740 fs/file_table.c:280
> ____fput+0x15/0x20 fs/file_table.c:313
> task_work_run+0x176/0x1b0 kernel/task_work.c:113
> tracehook_notify_resume include/linux/tracehook.h:188 [inline]
> exit_to_usermode_loop arch/x86/entry/common.c:164 [inline]
> prepare_exit_to_usermode+0x480/0x5b0 arch/x86/entry/common.c:195
> syscall_return_slowpath+0x113/0x4a0 arch/x86/entry/common.c:278
> do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:304
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8880a8d91800
> which belongs to the cache kmalloc-256 of size 256
> The buggy address is located 48 bytes inside of
> 256-byte region [ffff8880a8d91800, ffff8880a8d91900)
> The buggy address belongs to the page:
> page:ffffea0002a36440 refcount:1 mapcount:0 mapping:ffff8880aa4008c0 index:0x0
> flags: 0xfffe0000000200(slab)
> raw: 00fffe0000000200 ffffea000265d2c8 ffffea00022f7948 ffff8880aa4008c0
> raw: 0000000000000000 ffff8880a8d91000 0000000100000008 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff8880a8d91700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8880a8d91780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff8880a8d91800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff8880a8d91880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a8d91900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
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