==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff868889d8 of 8 bytes by task 12162 on cpu 1:
 data_alloc+0x31c/0x390 kernel/printk/printk_ringbuffer.c:1130
 prb_reserve+0x8d7/0xad0 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x53c/0x830 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x5c0 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 mnt_warn_timestamp_expiry+0x1c3/0x200 fs/namespace.c:3178
 do_new_mount_fc fs/namespace.c:3652 [inline]
 do_new_mount+0x31b/0x6a0 fs/namespace.c:3712
 path_mount+0x4ab/0xb80 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff868889d8 of 8 bytes by task 12158 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:792 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:938 [inline]
 prb_reserve+0x207/0xad0 kernel/printk/printk_ringbuffer.c:1674
 vprintk_store+0x53c/0x830 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x5c0 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __ext4_msg+0x135/0x1a0 fs/ext4/super.c:992
 ext4_check_quota_consistency fs/ext4/super.c:-1 [inline]
 ext4_check_opt_consistency+0xb05/0xb10 fs/ext4/super.c:2816
 __ext4_fill_super fs/ext4/super.c:5350 [inline]
 ext4_fill_super+0x1b06/0x37a0 fs/ext4/super.c:5777
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1691
 get_tree_bdev+0x1f/0x30 fs/super.c:1714
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5809
 vfs_get_tree+0x57/0x1d0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x24d/0x6a0 fs/namespace.c:3712
 path_mount+0x4ab/0xb80 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000186d30 -> 0x0000000000232d70

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 12158 Comm: syz.5.12767 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
EXT4-fs: Journaled quota options ignored when QUOTA feature is enabled
EXT4-fs (loop5): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /133/bus supports timestamps until 2038-01-19 (0x7fffffff)
EXT4-fs error (device loop5): ext4_do_update_inode:5617: inode #18: comm syz.5.12767: corrupted inode contents
EXT4-fs error (device loop5): ext4_dirty_inode:6502: inode #18: comm syz.5.12767: mark_inode_dirty error
EXT4-fs error (device loop5): ext4_do_update_inode:5617: inode #18: comm syz.5.12767: corrupted inode contents
EXT4-fs error (device loop5): ext4_xattr_delete_inode:3000: inode #18: comm syz.5.12767: mark_inode_dirty error
EXT4-fs error (device loop5): ext4_xattr_delete_inode:3003: inode #18: comm syz.5.12767: mark inode dirty (error -117)
EXT4-fs warning (device loop5): ext4_evict_inode:273: xattr delete (err -117)