KCSAN: data-race in __follow_mount_rcu.isra.0 / vfs_unlink

Status: auto-closed as invalid on 2020/06/18 13:11
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+cd0a37636a43c0ae81d1@syzkaller.appspotmail.com
First crash: 2362d, last: 2315d

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __follow_mount_rcu.isra.0 / vfs_unlink

write to 0xffff8881251c63c0 of 4 bytes by task 4913 on cpu 1:
 dont_mount include/linux/dcache.h:352 [inline]
 vfs_unlink+0x267/0x3e0 fs/namei.c:4075
 do_unlinkat+0x33f/0x550 fs/namei.c:4137
 __do_sys_unlink fs/namei.c:4184 [inline]
 __se_sys_unlink fs/namei.c:4182 [inline]
 __x64_sys_unlink+0x38/0x50 fs/namei.c:4182
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881251c63c0 of 4 bytes by task 4031 on cpu 0:
 managed_dentry_rcu fs/namei.c:1381 [inline]
 __follow_mount_rcu.isra.0+0x5a/0x330 fs/namei.c:1398
 lookup_fast+0x249/0x6e0 fs/namei.c:1700
 walk_component+0x73/0x9a0 fs/namei.c:1911
 lookup_last fs/namei.c:2391 [inline]
 path_lookupat.isra.0+0x129/0x2e0 fs/namei.c:2436
 filename_lookup+0x145/0x2b0 fs/namei.c:2466
 user_path_at_empty+0x47/0x60 fs/namei.c:2746
 do_readlinkat+0x89/0x230 fs/stat.c:409
 __do_sys_readlink fs/stat.c:442 [inline]
 __se_sys_readlink fs/stat.c:439 [inline]
 __x64_sys_readlink+0x4c/0x60 fs/stat.c:439
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4031 Comm: udevd Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/04/09 17:27 https://github.com/google/ktsan.git kcsan 40959e34d670 a8c6a3f8 .config console log report ci2-upstream-kcsan-gce
2020/04/09 13:38 https://github.com/google/ktsan.git kcsan 40959e34d670 a8c6a3f8 .config console log report ci2-upstream-kcsan-gce
2020/04/07 05:06 https://github.com/google/ktsan.git kcsan 40959e34d670 99a96044 .config console log report ci2-upstream-kcsan-gce
2020/03/25 23:16 https://github.com/google/ktsan.git kcsan 40959e34d670 e8e6c7d2 .config console log report ci2-upstream-kcsan-gce
2020/03/18 13:47 https://github.com/google/ktsan.git kcsan 941e0d917bbf 0a96a13c .config console log report ci2-upstream-kcsan-gce
2020/03/10 03:44 https://github.com/google/ktsan.git kcsan 941e0d917bbf 35f53e45 .config console log report ci2-upstream-kcsan-gce
2020/03/08 11:18 https://github.com/google/ktsan.git kcsan 941e0d917bbf 2e9971bb .config console log report ci2-upstream-kcsan-gce
2020/03/04 17:59 https://github.com/google/ktsan.git kcsan 766d004d1b85 712198ac .config console log report ci2-upstream-kcsan-gce
2020/02/26 19:30 https://github.com/google/ktsan.git kcsan 766d004d1b85 251aabb7 .config console log report ci2-upstream-kcsan-gce
2020/02/25 09:44 https://github.com/google/ktsan.git kcsan 766d004d1b85 59b57593 .config console log report ci2-upstream-kcsan-gce
2020/02/25 08:10 https://github.com/google/ktsan.git kcsan 766d004d1b85 59b57593 .config console log report ci2-upstream-kcsan-gce
2020/02/25 04:30 https://github.com/google/ktsan.git kcsan 766d004d1b85 59b57593 .config console log report ci2-upstream-kcsan-gce
2020/02/23 07:03 https://github.com/google/ktsan.git kcsan 766d004d1b85 2c36e7a7 .config console log report ci2-upstream-kcsan-gce
* Struck through repros no longer work on HEAD.