syzbot

loop4: detected capacity change from 0 to 128
==================================================================
BUG: KCSAN: data-race in __mark_inode_dirty / __mark_inode_dirty

write to 0xffff8881198c3a28 of 4 bytes by task 10969 on cpu 0:
 __mark_inode_dirty+0x248/0x750 fs/fs-writeback.c:2597
 fat_update_time+0x1ec/0x200 fs/fat/misc.c:357
 inode_update_time fs/inode.c:2129 [inline]
 touch_atime+0x148/0x340 fs/inode.c:2202
 file_accessed include/linux/fs.h:2673 [inline]
 filemap_splice_read+0x6ba/0x740 mm/filemap.c:3083
 do_splice_read fs/splice.c:982 [inline]
 splice_direct_to_actor+0x26f/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+0x2bb4/0x3000 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

read to 0xffff8881198c3a28 of 4 bytes by task 10962 on cpu 1:
 __mark_inode_dirty+0x55/0x750 fs/fs-writeback.c:2548
 fat_update_time+0x1ec/0x200 fs/fat/misc.c:357
 inode_update_time fs/inode.c:2129 [inline]
 touch_atime+0x148/0x340 fs/inode.c:2202
 file_accessed include/linux/fs.h:2673 [inline]
 filemap_splice_read+0x6ba/0x740 mm/filemap.c:3083
 do_splice_read fs/splice.c:982 [inline]
 splice_direct_to_actor+0x26f/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+0x2bb4/0x3000 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: 0x00000000 -> 0x00000070

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10962 Comm: syz.4.2595 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================
syz.4.2595: attempt to access beyond end of device
loop4: rw=2049, sector=128, nr_sectors = 1 limit=128
Buffer I/O error on dev loop4, logical block 128, lost async page write