syzbot


KASAN: use-after-free Read in afs_deactivate_cell (2)

Status: fixed on 2020/11/16 12:12
Subsystems: afs
[Documentation on labels]
Reported-by: syzbot+a5e4946b04d6ca8fa5f3@syzkaller.appspotmail.com
Fix commit: 1d0e850a49a5 afs: Fix cell removal
First crash: 1391d, last: 1372d
Cause bisection: introduced by (bisect log) :
commit 13fcc6837049f1bd76d57e9abc217a91fdbad764
Author: David Howells <dhowells@redhat.com>
Date: Thu Nov 1 23:07:27 2018 +0000

  afs: Add fs_context support

Crash: KASAN: use-after-free Read in __d_alloc (log)
Repro: C syz .config
  
Discussions (3)
Title Replies (including bot) Last reply
[PATCH 5.9 000/757] 5.9.2-rc1 review 766 (766) 2020/10/30 08:32
[PATCH 5.8 000/633] 5.8.17-rc1 review 638 (638) 2020/10/28 22:08
KASAN: use-after-free Read in afs_deactivate_cell (2) 0 (3) 2020/09/30 19:03
Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in afs_deactivate_cell afs 1 1597d 1594d 0/27 auto-closed as invalid on 2020/04/27 10:28

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __hlist_del include/linux/list.h:826 [inline]
BUG: KASAN: use-after-free in hlist_del_rcu include/linux/rculist.h:514 [inline]
BUG: KASAN: use-after-free in afs_deactivate_cell+0x165/0x1a0 fs/afs/cell.c:647
Read of size 8 at addr ffff888093021080 by task kworker/0:3/2653

CPU: 0 PID: 2653 Comm: kworker/0:3 Not tainted 5.9.0-rc7-next-20200929-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: afs afs_manage_cell
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fb lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
 __hlist_del include/linux/list.h:826 [inline]
 hlist_del_rcu include/linux/rculist.h:514 [inline]
 afs_deactivate_cell+0x165/0x1a0 fs/afs/cell.c:647
 afs_manage_cell+0x326/0x11c0 fs/afs/cell.c:721
 process_one_work+0x933/0x15a0 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3af/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Allocated by task 7905:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x1a0/0x480 mm/slab.c:3552
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 afs_alloc_cell fs/afs/cell.c:151 [inline]
 afs_lookup_cell+0x5b8/0x1450 fs/afs/cell.c:262
 afs_parse_source fs/afs/super.c:290 [inline]
 afs_parse_param+0x404/0x8c0 fs/afs/super.c:326
 vfs_parse_fs_param fs/fs_context.c:117 [inline]
 vfs_parse_fs_param+0x203/0x550 fs/fs_context.c:98
 vfs_parse_fs_string+0xe6/0x150 fs/fs_context.c:161
 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:201
 do_new_mount fs/namespace.c:2892 [inline]
 path_mount+0x1266/0x1e70 fs/namespace.c:3227
 __do_sys_mount fs/namespace.c:3438 [inline]
 __se_sys_mount fs/namespace.c:3411 [inline]
 __x64_sys_mount+0x278/0x2f0 fs/namespace.c:3411
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 2653:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3420 [inline]
 kfree+0x10e/0x2a0 mm/slab.c:3758
 rcu_do_batch kernel/rcu/tree.c:2481 [inline]
 rcu_core+0x645/0x1240 kernel/rcu/tree.c:2715
 __do_softirq+0x203/0xab6 kernel/softirq.c:298

Last call_rcu():
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_record_aux_stack+0x82/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2957 [inline]
 call_rcu+0x15e/0x7d0 kernel/rcu/tree.c:3030
 afs_manage_cell+0x250/0x11c0 fs/afs/cell.c:751
 process_one_work+0x933/0x15a0 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3af/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

The buggy address belongs to the object at ffff888093021000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 128 bytes inside of
 1024-byte region [ffff888093021000, ffff888093021400)
The buggy address belongs to the page:
page:00000000fb0f011a refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x93021
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002992c48 ffffea000249fd08 ffff8880aa040700
raw: 0000000000000000 ffff888093021000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888093020f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888093021000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888093021080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888093021100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888093021180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/09/30 08:24 linux-next 49e7e3e905e4 5abc3f1a .config console log report syz C ci-upstream-linux-next-kasan-gce-root
2020/10/09 12:08 upstream 583090b1b823 92390980 .config console log report info ci-upstream-kasan-gce-selinux-root
2020/09/26 15:55 upstream 7c7ec3226f5f 2d5ea0cb .config console log report info ci-upstream-kasan-gce-root
2020/09/25 02:18 upstream 171d4ff79f96 54289b08 .config console log report info ci-upstream-kasan-gce-root
2020/09/24 07:16 upstream c9c9e6a49f89 54289b08 .config console log report info ci-upstream-kasan-gce-selinux-root
2020/09/22 15:19 upstream 98477740630f 3e8f6c27 .config console log report info ci-upstream-kasan-gce-root
2020/09/20 12:59 upstream 325d0eab4f31 53ce8104 .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/05 04:54 upstream 549738f15da0 5ef9c291 .config console log report info ci-upstream-kasan-gce-386
2020/09/22 12:24 upstream 98477740630f 3e8f6c27 .config console log report info ci-qemu-upstream-386
2020/09/22 16:10 linux-next e64997027d5f 3e8f6c27 .config console log report info ci-upstream-linux-next-kasan-gce-root
2020/09/22 15:33 linux-next e64997027d5f 3e8f6c27 .config console log report info ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.