syzbot


KASAN: use-after-free Read in tctx_task_work

Status: fixed on 2021/04/09 19:46
Reported-by: syzbot+a157ac7c03a56397f553@syzkaller.appspotmail.com
Fix commit: 2c32395d8111 io_uring: fix __tctx_task_work() ctx race
First crash: 491d, last: 489d
similar bugs (1):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in tctx_task_work (2) C unreliable 353 1d09h 314d 0/22 upstream: reported C repro on 2021/08/19 08:10

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __tctx_task_work fs/io_uring.c:2217 [inline]
BUG: KASAN: use-after-free in tctx_task_work+0x238/0x280 fs/io_uring.c:2230
Read of size 4 at addr ffff88802178e3f0 by task syz-executor.2/12656

CPU: 1 PID: 12656 Comm: syz-executor.2 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x125/0x19e lib/dump_stack.c:120
 print_address_description+0x5f/0x3a0 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:397 [inline]
 kasan_report+0x15e/0x200 mm/kasan/report.c:414
 __tctx_task_work fs/io_uring.c:2217 [inline]
 tctx_task_work+0x238/0x280 fs/io_uring.c:2230
 task_work_run+0x146/0x1c0 kernel/task_work.c:140
 exit_task_work include/linux/task_work.h:30 [inline]
 do_exit+0x6e4/0x2380 kernel/exit.c:825
 do_group_exit+0x168/0x2d0 kernel/exit.c:922
 get_signal+0x1734/0x1ef0 kernel/signal.c:2773
 arch_do_signal_or_restart+0x3c/0x610 arch/x86/kernel/signal.c:811
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0xac/0x1e0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x48/0x180 kernel/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x465ef9
Code: Unable to access opcode bytes at RIP 0x465ecf.
RSP: 002b:00007f80563b5188 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: 0000000000000302 RBX: 000000000056c008 RCX: 0000000000465ef9
RDX: 0000000000000000 RSI: 0000000000000302 RDI: 0000000000000003
RBP: 00000000004bcd1c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008
R13: 00007ffedb23021f R14: 00007f80563b5300 R15: 0000000000022000

Allocated by task 12638:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:400 [inline]
 ____kasan_kmalloc+0xbd/0xf0 mm/kasan/common.c:428
 kasan_kmalloc include/linux/kasan.h:218 [inline]
 kmem_cache_alloc_trace+0x205/0x300 mm/slub.c:2922
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:684 [inline]
 io_ring_ctx_alloc fs/io_uring.c:1316 [inline]
 io_uring_create fs/io_uring.c:9745 [inline]
 io_uring_setup fs/io_uring.c:9876 [inline]
 __do_sys_io_uring_setup fs/io_uring.c:9882 [inline]
 __se_sys_io_uring_setup+0x368/0x3140 fs/io_uring.c:9879
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 54:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x3d/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:356
 ____kasan_slab_free+0xd3/0x110 mm/kasan/common.c:361
 kasan_slab_free include/linux/kasan.h:191 [inline]
 slab_free_hook mm/slub.c:1561 [inline]
 slab_free_freelist_hook+0xdd/0x1b0 mm/slub.c:1594
 slab_free mm/slub.c:3146 [inline]
 kfree+0xcf/0x2b0 mm/slub.c:4182
 process_one_work+0x789/0xfd0 kernel/workqueue.c:2275
 worker_thread+0xac1/0x1300 kernel/workqueue.c:2421
 kthread+0x39a/0x3c0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Last potentially related work creation:
 kasan_save_stack+0x27/0x50 mm/kasan/common.c:38
 kasan_record_aux_stack+0xcc/0x100 mm/kasan/generic.c:344
 insert_work+0x54/0x400 kernel/workqueue.c:1331
 __queue_work+0x97f/0xcc0 kernel/workqueue.c:1497
 queue_work_on+0xb5/0x100 kernel/workqueue.c:1524
 io_uring_release+0x57/0x70 fs/io_uring.c:8895
 __fput+0x352/0x7b0 fs/file_table.c:280
 task_work_run+0x146/0x1c0 kernel/task_work.c:140
 exit_task_work include/linux/task_work.h:30 [inline]
 do_exit+0x6e4/0x2380 kernel/exit.c:825
 do_group_exit+0x168/0x2d0 kernel/exit.c:922
 get_signal+0x1734/0x1ef0 kernel/signal.c:2773
 arch_do_signal_or_restart+0x3c/0x610 arch/x86/kernel/signal.c:811
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0xac/0x1e0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x48/0x180 kernel/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88802178e000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1008 bytes inside of
 4096-byte region [ffff88802178e000, ffff88802178f000)
The buggy address belongs to the page:
page:00000000f7d94ef1 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x21788
head:00000000f7d94ef1 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888011042140
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88802178e280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802178e300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802178e380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff88802178e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802178e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (2):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce-smack-root 2021/02/25 15:31 upstream 29c395c77a9a 76f7fc95 .config log report info KASAN: use-after-free Read in tctx_task_work
ci-upstream-kasan-gce-386 2021/02/23 17:47 upstream 3b9cdafb5358 fcc6d71b .config log report info KASAN: use-after-free Read in tctx_task_work