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KASAN: use-after-free Read in percpu_ref_switch_to_atomic_rcu

Status: fixed on 2020/04/15 17:19
Subsystems: block
[Documentation on labels]
Reported-by: syzbot+e017e49c39ab484ac87a@syzkaller.appspotmail.com
Fix commit: c1e2148f8ecb io_uring: free fixed_file_data after RCU grace period
First crash: 1402d, last: 1379d
Discussions (1)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in percpu_ref_switch_to_atomic_rcu 12 (13) 2020/03/06 17:21

Sample crash report:
==================================================================
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+0x4a3/0x540 lib/percpu-refcount.c:165
Read of size 1 at addr ffff888096139230 by task syz-executor.4/12677

CPU: 1 PID: 12677 Comm: syz-executor.4 Not tainted 5.6.0-rc3-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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
 kasan_report+0x12/0x20 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+0x4a3/0x540 lib/percpu-refcount.c:165
 rcu_do_batch kernel/rcu/tree.c:2186 [inline]
 rcu_core+0x5e1/0x1390 kernel/rcu/tree.c:2410
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2419
 __do_softirq+0x262/0x98c kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x19b/0x1e0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:546 [inline]
 smp_apic_timer_interrupt+0x1a3/0x610 arch/x86/kernel/apic/apic.c:1146
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:kfree+0x239/0x2c0 mm/slab.c:3758
Code: 4e 7e 0f 85 20 fe ff ff e8 55 8b 4c ff e9 16 fe ff ff e8 3a 42 c7 ff 48 83 3d ca d1 ff 07 00 0f 84 85 00 00 00 48 89 df 57 9d <0f> 1f 44 00 00 5b 41 5c 41 5d 41 5e 5d c3 e8 14 42 c7 ff 48 83 3d
RSP: 0018:ffffc900048efd10 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000007 RBX: 0000000000000286 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000286
RBP: ffffc900048efd30 R08: 1ffffffff16a3575 R09: fffffbfff16a3576
R10: fffffbfff16a3575 R11: ffffffff8b51abaf R12: ffff888218977f40
R13: ffff8880aa4001c0 R14: ffffffff83934479 R15: ffff888218a2f080
 disk_release+0x149/0x300 block/genhd.c:1329
 device_release+0x7a/0x210 drivers/base/core.c:1358
 kobject_cleanup lib/kobject.c:693 [inline]
 kobject_release lib/kobject.c:722 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1ff/0x2e0 lib/kobject.c:739
 put_disk+0x23/0x30 block/genhd.c:1545
 loop_remove+0x99/0xd0 drivers/block/loop.c:2095
 loop_control_ioctl drivers/block/loop.c:2191 [inline]
 loop_control_ioctl+0x320/0x360 drivers/block/loop.c:2157
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x123/0x180 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c449
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f0f739c7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0f739c86d4 RCX: 000000000045c449
RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 000000000000000b
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000003ee R14: 00000000004c641b R15: 000000000076bf2c

Allocated by task 12676:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:515 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x163/0x770 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc.constprop.0+0x1b/0x20 include/linux/slab.h:669
 io_sqe_files_register fs/io_uring.c:5634 [inline]
 __io_uring_register+0xad7/0x2f40 fs/io_uring.c:7096
 __do_sys_io_uring_register fs/io_uring.c:7176 [inline]
 __se_sys_io_uring_register fs/io_uring.c:7158 [inline]
 __x64_sys_io_uring_register+0x1a1/0x560 fs/io_uring.c:7158
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 12675:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 io_sqe_files_unregister+0x203/0x2f0 fs/io_uring.c:5346
 io_ring_ctx_free fs/io_uring.c:6335 [inline]
 io_ring_ctx_wait_and_kill+0x4ed/0xa60 fs/io_uring.c:6426
 io_uring_release+0x42/0x50 fs/io_uring.c:6434
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888096139200
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 48 bytes inside of
 256-byte region [ffff888096139200, ffff888096139300)
The buggy address belongs to the page:
page:ffffea0002584e40 refcount:1 mapcount:0 mapping:ffff8880aa4008c0 index:0xffff888096139600
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000263cf48 ffffea00025302c8 ffff8880aa4008c0
raw: ffff888096139600 ffff888096139000 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888096139100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888096139180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888096139200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888096139280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888096139300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/02/29 18:11 upstream f8788d86ab28 59b57593 .config console log report ci-upstream-kasan-gce-root
2020/02/09 10:42 upstream fdfa3a6778b1 6ece2ea5 .config console log report ci-upstream-kasan-gce
2020/02/06 06:29 upstream 4c7d00ccf40d 662cf49a .config console log report ci-upstream-kasan-gce-smack-root
2020/02/06 04:10 upstream 4c7d00ccf40d 662cf49a .config console log report ci-upstream-kasan-gce
2020/02/17 17:26 linux-next c25a951c50dc 2b411596 .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.