KASAN: use-after-free Read in afs_manage_cell

Status: fixed on 2020/11/16 12:12
Subsystems: afs
[Documentation on labels]
Fix commit: 1d0e850a49a5 afs: Fix cell removal
First crash: 1403d, last: 1388d
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_manage_cell 0 (1) 2020/09/21 10:32

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:487 [inline]
BUG: KASAN: use-after-free in afs_deactivate_cell fs/afs/cell.c:647 [inline]
BUG: KASAN: use-after-free in afs_manage_cell+0x256/0x1540 fs/afs/cell.c:721
Read of size 8 at addr ffff888098db6080 by task kworker/1:2/2547

CPU: 1 PID: 2547 Comm: kworker/1:2 Not tainted 5.9.0-rc8-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+0x1d6/0x29e lib/dump_stack.c:118
 print_address_description+0x66/0x620 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 __hlist_del include/linux/list.h:826 [inline]
 hlist_del_rcu include/linux/rculist.h:487 [inline]
 afs_deactivate_cell fs/afs/cell.c:647 [inline]
 afs_manage_cell+0x256/0x1540 fs/afs/cell.c:721
 process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
 process_scheduled_works kernel/workqueue.c:2331 [inline]
 worker_thread+0xde4/0x1460 kernel/workqueue.c:2417
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 14851:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x100/0x130 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x1e4/0x2e0 mm/slab.c:3554
 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+0x4ab/0x14d0 fs/afs/cell.c:262
 afs_parse_source fs/afs/super.c:290 [inline]
 afs_parse_param+0x526/0x790 fs/afs/super.c:326
 vfs_parse_fs_param+0x1e5/0x460 fs/fs_context.c:117
 vfs_parse_fs_string fs/fs_context.c:161 [inline]
 generic_parse_monolithic+0x230/0x350 fs/fs_context.c:201
 do_new_mount fs/namespace.c:2871 [inline]
 path_mount+0x176c/0x29e0 fs/namespace.c:3192
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount+0x126/0x180 fs/namespace.c:3390
 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46

Freed by task 2547:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
 kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xdd/0x110 mm/kasan/common.c:422
 __cache_free mm/slab.c:3422 [inline]
 kfree+0x113/0x200 mm/slab.c:3760
 rcu_do_batch kernel/rcu/tree.c:2430 [inline]
 rcu_core+0x79b/0x1130 kernel/rcu/tree.c:2658
 __do_softirq+0x256/0x6d5 kernel/softirq.c:298

Last call_rcu():
 kasan_save_stack+0x27/0x50 mm/kasan/common.c:48
 kasan_record_aux_stack+0x7b/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2896 [inline]
 call_rcu+0x141/0x830 kernel/rcu/tree.c:2970
 afs_manage_cell+0xd7d/0x1540 fs/afs/cell.c:751
 process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
 worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff888098db6000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 128 bytes inside of
 1024-byte region [ffff888098db6000, ffff888098db6400)
The buggy address belongs to the page:
page:000000009b96ad2d refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x98db6
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00024ca6c8 ffffea00029cebc8 ffff8880aa440700
raw: 0000000000000000 ffff888098db6000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888098db5f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888098db6000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888098db6080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888098db6100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888098db6180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/10/06 02:32 upstream 7575fdda569b 1880b4a9 .config console log report info ci-upstream-kasan-gce-smack-root
2020/09/30 15:27 upstream 02de58b24d2e 8516f6d3 .config console log report info ci-upstream-kasan-gce-selinux-root
2020/09/27 06:10 upstream a1bffa48745a 5dd8aee8 .config console log report info ci-upstream-kasan-gce-selinux-root
2020/09/30 08:02 linux-next 49e7e3e905e4 5abc3f1a .config console log report info ci-upstream-linux-next-kasan-gce-root
2020/09/20 18:06 linux-next b652d2a5f2a4 9564d2e9 .config console log report info ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.