EXT4-fs (loop1): Free/Dirty block details
EXT4-fs (loop1): free_blocks=0
EXT4-fs (loop1): dirty_blocks=64
EXT4-fs (loop1): Block reservation details
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff893d05e9 of 15 bytes by task 19986 on cpu 1:
 vsnprintf+0x2c0/0x8c0 lib/vsprintf.c:2896
 va_format lib/vsprintf.c:1725 [inline]
 pointer+0x844/0xc90 lib/vsprintf.c:2573
 vsnprintf+0x49e/0x8c0 lib/vsprintf.c:2949
 vscnprintf+0x41/0x90 lib/vsprintf.c:3014
 printk_sprint+0x30/0x2b0 kernel/printk/printk.c:2222
 vprintk_store+0x57b/0x910 kernel/printk/printk.c:2364
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 logfc+0x2c0/0x2d0 fs/fs_context.c:-1
 fs_param_is_gid+0x161/0x240 fs/fs_parser.c:-1
 __fs_parse+0x30c/0x430 fs/fs_parser.c:128
 fs_parse include/linux/fs_parser.h:76 [inline]
 fat_parse_param+0xbe/0x7d0 fs/fat/inode.c:1174
 msdos_parse_param+0x1f/0x30 fs/fat/namei_msdos.c:670
 vfs_parse_fs_param+0x142/0x2a0 fs/fs_context.c:132
 vfs_parse_fs_qstr fs/fs_context.c:173 [inline]
 vfs_parse_fs_string include/linux/fs_context.h:142 [inline]
 vfs_parse_monolithic_sep+0x1e6/0x270 fs/fs_context.c:213
 generic_parse_monolithic+0x24/0x30 fs/fs_context.c:241
 parse_monolithic_mount_data+0x46/0x60 fs/fs_context.c:519
 do_new_mount+0x24e/0x8d0 fs/namespace.c:3837
 path_mount+0x4ad/0xb90 fs/namespace.c:4161
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4367
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4367
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff893d05f0 of 8 bytes by task 19973 on cpu 0:
 data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
 data_push_tail+0x104/0x440 kernel/printk/printk_ringbuffer.c:693
 data_alloc+0x111/0x380 kernel/printk/printk_ringbuffer.c:1089
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __ext4_msg+0x1aa/0x1c0 fs/ext4/super.c:1001
 ext4_print_free_blocks fs/ext4/inode.c:1802 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2527 [inline]
 ext4_do_writepages+0x1e72/0x2720 fs/ext4/inode.c:2949
 ext4_writepages+0x18f/0x300 fs/ext4/inode.c:3043
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 filemap_write_and_wait_range+0x166/0x370 mm/filemap.c:684
 filemap_invalidate_pages+0xd3/0x1e0 mm/filemap.c:2918
 kiocb_invalidate_pages+0x6e/0x80 mm/filemap.c:2937
 __iomap_dio_rw+0x6e7/0x1410 fs/iomap/direct-io.c:778
 iomap_dio_rw+0x40/0x90 fs/iomap/direct-io.c:903
 ext4_dio_write_iter fs/ext4/file.c:592 [inline]
 ext4_file_write_iter+0xc2d/0xef0 fs/ext4/file.c:733
 do_iter_readv_writev+0x4f6/0x5a0 fs/read_write.c:-1
 vfs_writev+0x2d1/0x8b0 fs/read_write.c:1058
 do_pwritev fs/read_write.c:1154 [inline]
 __do_sys_pwritev2 fs/read_write.c:1212 [inline]
 __se_sys_pwritev2+0xfc/0x1c0 fs/read_write.c:1203
 __x64_sys_pwritev2+0x67/0x80 fs/read_write.c:1203
 x64_sys_call+0xe07/0x3020 arch/x86/include/generated/asm/syscalls_64.h:329
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000001817 -> 0x69672720726f6620

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 19973 Comm: syz.1.4274 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================