syzbot

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BUG: KCSAN: data-race in touch_atime / touch_atime

write to 0xffff888119fcb828 of 4 bytes by task 13952 on cpu 0:
 inode_set_atime_to_ts include/linux/fs.h:1805 [inline]
 inode_update_timestamps fs/inode.c:2088 [inline]
 generic_update_time fs/inode.c:2110 [inline]
 inode_update_time fs/inode.c:2130 [inline]
 touch_atime+0x1e8/0x340 fs/inode.c:2202
 file_accessed include/linux/fs.h:2673 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3446
 new_sync_read fs/read_write.c:491 [inline]
 vfs_read+0x64c/0x770 fs/read_write.c:572
 ksys_read+0xda/0x1a0 fs/read_write.c:715
 __do_sys_read fs/read_write.c:724 [inline]
 __se_sys_read fs/read_write.c:722 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:722
 x64_sys_call+0x27c0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888119fcb828 of 4 bytes by task 14473 on cpu 1:
 inode_get_atime_nsec include/linux/fs.h:1790 [inline]
 inode_get_atime include/linux/fs.h:1796 [inline]
 inode_update_timestamps fs/inode.c:2085 [inline]
 generic_update_time fs/inode.c:2110 [inline]
 inode_update_time fs/inode.c:2130 [inline]
 touch_atime+0x194/0x340 fs/inode.c:2202
 file_accessed include/linux/fs.h:2673 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3446
 new_sync_read fs/read_write.c:491 [inline]
 vfs_read+0x64c/0x770 fs/read_write.c:572
 ksys_read+0xda/0x1a0 fs/read_write.c:715
 __do_sys_read fs/read_write.c:724 [inline]
 __se_sys_read fs/read_write.c:722 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:722
 x64_sys_call+0x27c0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x325cd5cd -> 0x327d130a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 14473 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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udevd[14473]: inotify_add_watch(7, /dev/loop7p4, 10) failed: No such file or directory