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KASAN: use-after-free Read in locks_delete_block

Status: fixed on 2019/01/15 20:25
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+a4a3d526b4157113ec6a@syzkaller.appspotmail.com
Fix commit: 16306a61d3b7 fs/locks: always delete_block after waiting.
First crash: 2424d, last: 2401d
▶ ▼ Duplicate bugs (6)
duplicates (6):
Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
KASAN: stack-out-of-bounds Read in locks_delete_block fs 1 2423d 2422d 0/29 closed as dup on 2018/11/16 20:38
BUG: unable to handle kernel paging request in locks_remove_file fs 4 2428d 2429d 0/29 closed as dup on 2018/11/16 20:43
KASAN: use-after-free Read in locks_remove_flock fs 9 2428d 2429d 0/29 closed as dup on 2018/11/16 20:42
KASAN: stack-out-of-bounds Read in locks_remove_flock fs 18 2428d 2429d 0/29 closed as dup on 2018/11/16 20:41
BUG: corrupted list in locks_delete_block fs C 4 2411d 2425d 0/29 closed as dup on 2018/11/16 20:40
general protection fault in locks_remove_flock fs C 181 2428d 2429d 0/29 closed as dup on 2018/11/16 20:45
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH 00/12 v6] fs/locks: avoid thundering-herd wake-ups 14 (14) 2018/11/30 16:34
KASAN: use-after-free Read in locks_delete_block 11 (13) 2018/11/20 13:23
▶ ▼ Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-54 KASAN: use-after-free Read in locks_delete_block C 3 1946d 1999d 1/2 fixed on 2021/10/12 13:38

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0xf1/0x100 lib/list_debug.c:51
Read of size 8 at addr ffff8801b27c7c70 by task syz-executor0/6767

CPU: 1 PID: 6767 Comm: syz-executor0 Not tainted 4.20.0-rc1-next-20181109+ #110
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 __list_del_entry_valid+0xf1/0x100 lib/list_debug.c:51
 __list_del_entry include/linux/list.h:117 [inline]
 list_del_init include/linux/list.h:159 [inline]
 __locks_delete_block fs/locks.c:683 [inline]
 locks_delete_block+0xce/0x3d0 fs/locks.c:716
 locks_mandatory_area+0x48b/0x6a0 fs/locks.c:1398
 locks_verify_truncate include/linux/fs.h:2361 [inline]
 do_sys_ftruncate+0x4b2/0x550 fs/open.c:190
 __do_sys_ftruncate fs/open.c:204 [inline]
 __se_sys_ftruncate fs/open.c:202 [inline]
 __x64_sys_ftruncate+0x59/0x80 fs/open.c:202
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4319e97c78 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000000000039 RDI: 0000000000000004
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4319e986d4
R13: 00000000004bde51 R14: 00000000004cd048 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0006c9f1c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 ffffffff06c90101 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b27c7b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801b27c7b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8801b27c7c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff8801b27c7c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801b27c7d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/11/13 19:57 linux-next 442b8cea2477 5f5f6d14 .config console log report syz ci-upstream-linux-next-kasan-gce-root
2018/12/05 19:09 linux-next 442b8cea2477 ac6c0578 .config console log report ci-upstream-linux-next-kasan-gce-root
2018/11/28 23:42 linux-next 442b8cea2477 4b6d14f2 .config console log report ci-upstream-linux-next-kasan-gce-root
2018/11/12 19:01 linux-next 442b8cea2477 7b5f8621 .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.