syzbot

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BUG: KCSAN: data-race in filemap_read / filemap_read

read to 0xffff88811bc6eee8 of 8 bytes by task 10674 on cpu 0:
 filemap_read+0x6f/0xa00 mm/filemap.c:2686
 generic_file_read_iter+0x79/0x330 mm/filemap.c:2904
 ext4_file_read_iter+0x1cc/0x290 fs/ext4/file.c:-1
 copy_splice_read+0x43f/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 0xffff88811bc6eee8 of 8 bytes by task 10668 on cpu 1:
 filemap_read+0x974/0xa00 mm/filemap.c:2785
 generic_file_read_iter+0x79/0x330 mm/filemap.c:2904
 ext4_file_read_iter+0x1cc/0x290 fs/ext4/file.c:-1
 copy_splice_read+0x43f/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: 0x0000000000000327 -> 0x0000000000000328

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10668 Comm: syz.3.1042 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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