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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86c7b3e8 of 8 bytes by task 3993 on cpu 1:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8d7/0xae0 kernel/printk/printk_ringbuffer.c:1724
 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
 seq_buf_do_printk+0x113/0x1a0 lib/seq_buf.c:126
 mem_cgroup_print_oom_meminfo+0x17d/0x260 mm/memcontrol.c:1617
 dump_header+0xa2/0x240 mm/oom_kill.c:469
 oom_kill_process+0x295/0x350 mm/oom_kill.c:1047
 out_of_memory+0x97d/0xb80 mm/oom_kill.c:1185
 mem_cgroup_out_of_memory mm/memcontrol.c:1695 [inline]
 mem_cgroup_oom mm/memcontrol.c:1718 [inline]
 try_charge_memcg+0x62e/0xa10 mm/memcontrol.c:2456
 obj_cgroup_charge_pages+0x23/0xc0 mm/memcontrol.c:2857
 obj_cgroup_charge_account+0x73/0x1a0 mm/memcontrol.c:3160
 __memcg_slab_post_alloc_hook+0x392/0x540 mm/memcontrol.c:3249
 memcg_slab_post_alloc_hook mm/slub.c:2457 [inline]
 slab_post_alloc_hook mm/slub.c:4549 [inline]
 slab_alloc_node mm/slub.c:4866 [inline]
 kmem_cache_alloc_noprof+0x1e2/0x400 mm/slub.c:4873
 alloc_buffer_head+0x35/0x1f0 fs/buffer.c:3026
 folio_alloc_buffers+0x149/0x310 fs/buffer.c:932
 create_empty_buffers+0x2c/0x200 fs/buffer.c:1688
 folio_create_buffers fs/buffer.c:1799 [inline]
 __block_write_begin_int+0x1d4/0xf90 fs/buffer.c:2123
 block_page_mkwrite+0x1a8/0x3c0 fs/buffer.c:2636
 ext4_page_mkwrite+0x859/0xb90 fs/ext4/inode.c:6682
 do_page_mkwrite mm/memory.c:3589 [inline]
 do_shared_fault mm/memory.c:5875 [inline]
 do_fault mm/memory.c:5937 [inline]
 do_pte_missing mm/memory.c:4477 [inline]
 handle_pte_fault mm/memory.c:6317 [inline]
 __handle_mm_fault mm/memory.c:6455 [inline]
 handle_mm_fault+0x1904/0x3020 mm/memory.c:6624
 do_user_addr_fault+0x3fd/0x1050 arch/x86/mm/fault.c:1385
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffffffff86c7b3e8 of 16 bytes by task 2990 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x950 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 syslog_print+0x109/0x560 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2990 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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