syzbot

==================================================================
BUG: KCSAN: data-race in atime_needs_update / touch_atime

read to 0xffff8881aef0f258 of 4 bytes by task 13569 on cpu 1:
 atime_needs_update+0x25f/0x3e0 fs/inode.c:-1
 touch_atime+0x4a/0x340 fs/inode.c:2131
 file_accessed include/linux/fs.h:2663 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3508
 copy_splice_read+0x442/0x660 fs/splice.c:363
 do_splice_read fs/splice.c:981 [inline]
 splice_direct_to_actor+0x290/0x680 fs/splice.c:1086
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
 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

write to 0xffff8881aef0f258 of 4 bytes by task 13575 on cpu 0:
 inode_set_atime_to_ts include/linux/fs.h:1687 [inline]
 inode_update_timestamps fs/inode.c:2034 [inline]
 generic_update_time fs/inode.c:2056 [inline]
 inode_update_time fs/inode.c:2076 [inline]
 touch_atime+0x1e8/0x340 fs/inode.c:2148
 file_accessed include/linux/fs.h:2663 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3508
 copy_splice_read+0x442/0x660 fs/splice.c:363
 do_splice_read fs/splice.c:981 [inline]
 splice_direct_to_actor+0x290/0x680 fs/splice.c:1086
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 x64_sys_call+0x2bb0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:41
 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: 0x2546c99c -> 0x25d3a04d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 13575 Comm: syz.1.13614 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================