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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86c6ce70 of 8 bytes by task 18135 on cpu 0:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8d6/0xad0 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
 fserror_report+0x3bb/0x500 fs/fserror.c:178
 fserror_report_file_metadata include/linux/fserror.h:61 [inline]
 __ext4_error_inode+0x185/0x3c0 fs/ext4/super.c:867
 ext4_do_update_inode fs/ext4/inode.c:5690 [inline]
 ext4_mark_iloc_dirty+0x35e/0xd80 fs/ext4/inode.c:6352
 __ext4_mark_inode_dirty+0x2e0/0x3d0 fs/ext4/inode.c:6558
 ext4_dirty_inode+0x92/0xc0 fs/ext4/inode.c:6587
 __mark_inode_dirty+0x16f/0x710 fs/fs-writeback.c:2623
 mark_inode_dirty_sync include/linux/fs.h:2218 [inline]
 dquot_free_space include/linux/quotaops.h:373 [inline]
 dquot_free_block include/linux/quotaops.h:383 [inline]
 ext4_mb_clear_bb fs/ext4/mballoc.c:6662 [inline]
 ext4_free_blocks+0xea9/0x1430 fs/ext4/mballoc.c:6782
 ext4_xattr_release_block+0x38d/0x550 fs/ext4/xattr.c:1319
 ext4_xattr_delete_inode+0x6fd/0x7a0 fs/ext4/xattr.c:2994
 ext4_evict_inode+0xb16/0xe30 fs/ext4/inode.c:284
 evict+0x2af/0x510 fs/inode.c:841
 iput_final fs/inode.c:1960 [inline]
 iput+0x41a/0x580 fs/inode.c:2009
 ext4_process_orphan+0x1a9/0x1c0 fs/ext4/orphan.c:358
 ext4_orphan_cleanup+0x69c/0x9f0 fs/ext4/orphan.c:472
 __ext4_fill_super fs/ext4/super.c:5701 [inline]
 ext4_fill_super+0x3408/0x37c0 fs/ext4/super.c:5824
 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:5856
 vfs_get_tree+0x57/0x1d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3758 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3834
 path_mount+0x4d0/0xbc0 fs/namespace.c:4154
 do_mount fs/namespace.c:4167 [inline]
 __do_sys_mount fs/namespace.c:4383 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4360
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4360
 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/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c6ce70 of 16 bytes by task 2971 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1934 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1982 [inline]
 _prb_read_valid+0x1b6/0x950 kernel/printk/printk_ringbuffer.c:2173
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 syslog_print+0x164/0x560 kernel/printk/printk.c:1611
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1763
 __do_sys_syslog kernel/printk/printk.c:1855 [inline]
 __se_sys_syslog kernel/printk/printk.c:1853 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1853
 x64_sys_call+0x2b9e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2971 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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