syzbot

loop1: detected capacity change from 0 to 128
==================================================================
BUG: KCSAN: data-race in __mark_inode_dirty / __mark_inode_dirty

write to 0xffff888104e24728 of 4 bytes by task 12956 on cpu 0:
 __mark_inode_dirty+0x24e/0x7e0 fs/fs-writeback.c:2546
 mark_buffer_dirty+0x149/0x230 fs/buffer.c:1199
 __block_commit_write fs/buffer.c:2189 [inline]
 block_write_end+0x123/0x210 fs/buffer.c:2265
 generic_write_end+0x5c/0x160 fs/buffer.c:2279
 fat_write_end+0x4e/0x160 fs/fat/inode.c:242
 generic_perform_write+0x31e/0x4b0 mm/filemap.c:4123
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4219
 generic_file_write_iter+0x92/0x310 mm/filemap.c:4245
 iter_file_splice_write+0x5f2/0x980 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x160/0x2c0 fs/splice.c:1158
 splice_direct_to_actor+0x305/0x680 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xd9/0x150 fs/splice.c:1227
 do_sendfile+0x40a/0x690 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x113/0x160 fs/read_write.c:1415
 x64_sys_call+0xfc3/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104e24728 of 4 bytes by task 12949 on cpu 1:
 __mark_inode_dirty+0x58/0x7e0 fs/fs-writeback.c:2497
 fat_update_time+0x1e8/0x200 fs/fat/misc.c:357
 inode_update_time fs/inode.c:2076 [inline]
 touch_atime+0x14f/0x350 fs/inode.c:2149
 file_accessed include/linux/fs.h:2591 [inline]
 filemap_splice_read+0x8cb/0x930 mm/filemap.c:3036
 do_splice_read fs/splice.c:979 [inline]
 splice_direct_to_actor+0x26c/0x680 fs/splice.c:1083
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xd9/0x150 fs/splice.c:1227
 do_sendfile+0x40a/0x690 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x113/0x160 fs/read_write.c:1415
 x64_sys_call+0xfc3/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000008 -> 0x00000038

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12949 Comm: syz.1.3362 Not tainted 6.14.0-syzkaller-03576-g1e1ba8d23dae #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================