[moderation] [mm?] KCSAN: data-race in generic_fillattr / shmem_symlink (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1b8af6552cb7 Merge tag 'powerpc-6.7-3' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=162caffce80000
kernel config: https://syzkaller.appspot.com/x/.config?x=efc18f367a3f97fa
dashboard link: https://syzkaller.appspot.com/bug?extid=7e41441a470e45b69a19
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org hu...@google.com linux-...@vger.kernel.org linu...@kvack.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2dbebc9ea594/disk-1b8af655.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/41592181ba2a/vmlinux-1b8af655.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b72b3a6a43ae/bzImage-1b8af655.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7e4144...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in generic_fillattr / shmem_symlink

read-write to 0xffff888102a072c0 of 8 bytes by task 3190 on cpu 0:
shmem_symlink+0x31b/0x390 mm/shmem.c:3499
vfs_symlink+0xc2/0x1a0 fs/namei.c:4464
do_symlinkat+0xe3/0x340 fs/namei.c:4490
__do_sys_symlink fs/namei.c:4511 [inline]
__se_sys_symlink fs/namei.c:4509 [inline]
__x64_sys_symlink+0x56/0x60 fs/namei.c:4509
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888102a072c0 of 8 bytes by task 3690 on cpu 1:
i_size_read include/linux/fs.h:910 [inline]
generic_fillattr+0x144/0x2f0 fs/stat.c:59
shmem_getattr+0x17b/0x200 mm/shmem.c:1121
vfs_getattr_nosec fs/stat.c:135 [inline]
vfs_getattr+0x198/0x1e0 fs/stat.c:176
vfs_statx+0x12f/0x2f0 fs/stat.c:248
vfs_fstatat+0xcd/0x100 fs/stat.c:299
__do_sys_newfstatat fs/stat.c:463 [inline]
__se_sys_newfstatat+0x58/0x260 fs/stat.c:457
__x64_sys_newfstatat+0x55/0x60 fs/stat.c:457
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000000000dc -> 0x00000000000000f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3690 Comm: udevd Not tainted 6.7.0-rc3-syzkaller-00298-g1b8af6552cb7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================
udevd[3690]: inotify_add_watch(7, /dev/loop11, 10) failed: No such file or directory


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup