==================================================================
BUG: KCSAN: data-race in find_get_block_common / has_bh_in_lru

read-write to 0xffff888237d27778 of 8 bytes by task 17753 on cpu 1:
 bh_lru_install fs/buffer.c:1342 [inline]
 find_get_block_common+0x4ab/0x8a0 fs/buffer.c:1407
 bdev_getblk+0x4d/0x3f0 include/linux/gfp.h:-1
 __getblk include/linux/buffer_head.h:380 [inline]
 sb_getblk include/linux/buffer_head.h:386 [inline]
 fat_mirror_bhs+0x149/0x320 fs/fat/fatent.c:388
 fat_alloc_clusters+0xb48/0xc50 fs/fat/fatent.c:543
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x258/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x400/0xf90 fs/buffer.c:2142
 block_write_begin fs/buffer.c:2253 [inline]
 cont_write_begin+0x5fe/0x970 fs/buffer.c:2591
 fat_write_begin+0x4f/0xe0 fs/fat/inode.c:230
 generic_perform_write+0x183/0x490 mm/filemap.c:4314
 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4431
 generic_file_write_iter+0x8d/0x310 mm/filemap.c:4457
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:688
 ksys_write+0xdc/0x1a0 fs/read_write.c:740
 __do_sys_write fs/read_write.c:751 [inline]
 __se_sys_write fs/read_write.c:748 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:748
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237d27778 of 8 bytes by task 17781 on cpu 0:
 has_bh_in_lru+0x8c/0x1f0 fs/buffer.c:1548
 smp_call_function_many_cond+0x2c1/0xc30 kernel/smp.c:821
 on_each_cpu_cond_mask+0x3c/0x80 kernel/smp.c:1043
 on_each_cpu_cond include/linux/smp.h:106 [inline]
 invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1557
 kill_bdev block/bdev.c:90 [inline]
 set_blocksize+0x1e3/0x270 block/bdev.c:207
 sb_set_blocksize+0x93/0x170 block/bdev.c:240
 ext4_load_super fs/ext4/super.c:5167 [inline]
 __ext4_fill_super fs/ext4/super.c:5322 [inline]
 ext4_fill_super+0x148c/0x37c0 fs/ext4/super.c:5791
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1694
 get_tree_bdev+0x1f/0x30 fs/super.c:1717
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5823
 vfs_get_tree+0x57/0x1d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3760 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3836
 path_mount+0x4d0/0xbc0 fs/namespace.c:4146
 do_mount fs/namespace.c:4159 [inline]
 __do_sys_mount fs/namespace.c:4348 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4325
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4325
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff88811b50faf8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 17781 Comm: syz.9.3344 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================
EXT4-fs (loop9): orphan cleanup on readonly fs
EXT4-fs warning (device loop9): ext4_enable_quotas:7236: Failed to enable quota tracking (type=2, err=-22, ino=15). Please run e2fsck to fix.
EXT4-fs (loop9): Cannot turn on quotas: error -22
EXT4-fs error (device loop9): ext4_ext_check_inode:521: inode #13: comm syz.9.3344: pblk 0 bad header/extent: invalid extent entries - magic f30a, entries 1, max 4(4), depth 0(0)
loop9: lost file I/O error report for ino 13 type 5 pos 0x0 len 0x0 error -117
EXT4-fs error (device loop9): ext4_orphan_get:1396: comm syz.9.3344: couldn't read orphan inode 13 (err -117)
loop9: lost filesystem error report for type 5 error -117
EXT4-fs (loop9): mounted filesystem 00000000-0000-0000-0000-000000000000 ro without journal. Quota mode: writeback.
EXT4-fs (loop9): unmounting filesystem 00000000-0000-0000-0000-000000000000.