BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff868967d8 of 8 bytes by task 7013 on cpu 0:
 data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline]
 show_trace_log_lvl+0x4e3/0x560 arch/x86/kernel/dumpstack.c:282
 __dump_stack+0x1d/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0xe8/0x140 lib/dump_stack.c:120
 dump_stack+0x15/0x1b lib/dump_stack.c:129
 dump_header+0x81/0x220 mm/oom_kill.c:467
 oom_kill_process+0x342/0x400 mm/oom_kill.c:1040
 out_of_memory+0x979/0xb80 mm/oom_kill.c:1178
 mem_cgroup_out_of_memory mm/memcontrol.c:1649 [inline]
 mem_cgroup_oom mm/memcontrol.c:1672 [inline]
 try_charge_memcg+0x5e6/0x9e0 mm/memcontrol.c:2399
 try_charge mm/memcontrol.c:2499 [inline]
 charge_memcg+0x51/0xc0 mm/memcontrol.c:4702
 mem_cgroup_swapin_charge_folio+0xcc/0x150 mm/memcontrol.c:4788
 __read_swap_cache_async+0x1df/0x350 mm/swap_state.c:441
 swap_cluster_readahead+0x277/0x3e0 mm/swap_state.c:613
 swapin_readahead+0xde/0x6f0 mm/swap_state.c:811
 do_swap_page+0x301/0x2430 mm/memory.c:4586
 handle_pte_fault mm/memory.c:6055 [inline]
 __handle_mm_fault mm/memory.c:6195 [inline]
 handle_mm_fault+0x9a5/0x2c20 mm/memory.c:6364
 do_user_addr_fault+0x630/0x1080 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffffffff868967d8 of 8 bytes by task 7035 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline]
 prb_reserve+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 __ext4_error_inode+0x2ca/0x3f0 fs/ext4/super.c:844
 __ext4_mark_inode_dirty+0xbd/0x3f0 fs/ext4/inode.c:6512
 ext4_dirty_inode+0x92/0xc0 fs/ext4/inode.c:6538
 __mark_inode_dirty+0x15f/0x750 fs/fs-writeback.c:2566
 mark_inode_dirty_sync include/linux/fs.h:2609 [inline]
 dquot_free_space include/linux/quotaops.h:380 [inline]
 dquot_free_block include/linux/quotaops.h:390 [inline]
 ext4_xattr_release_block+0x51f/0x550 fs/ext4/xattr.c:1344
 ext4_xattr_delete_inode+0x6f3/0x790 fs/ext4/xattr.c:2984
 ext4_evict_inode+0xa6a/0xd90 fs/ext4/inode.c:271
 evict+0x2e3/0x550 fs/inode.c:810
 iput_final fs/inode.c:1914 [inline]
 iput+0x4ed/0x650 fs/inode.c:1966
 ext4_ext_migrate+0x8fe/0x9b0 fs/ext4/migrate.c:588
 __ext4_ioctl fs/ext4/ioctl.c:1402 [inline]
 ext4_ioctl+0xf78/0x2080 fs/ext4/ioctl.c:1626
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1816/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000127590 -> 0x00000000001eb898

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7035 Comm: syz.1.11096 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================
EXT4-fs error (device loop1): ext4_dirty_inode:6538: inode #20: comm syz.1.11096: mark_inode_dirty error
EXT4-fs error (device loop1): ext4_do_update_inode:5653: inode #20: comm syz.1.11096: corrupted inode contents
EXT4-fs error (device loop1): ext4_xattr_delete_inode:2991: inode #20: comm syz.1.11096: mark_inode_dirty error
EXT4-fs error (device loop1): ext4_xattr_delete_inode:2994: inode #20: comm syz.1.11096: mark inode dirty (error -117)
EXT4-fs warning (device loop1): ext4_evict_inode:274: xattr delete (err -117)