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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86876778 of 8 bytes by task 18893 on cpu 1:
 data_alloc+0x271/0x2b0 kernel/printk/printk_ringbuffer.c:1095
 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
 seq_buf_do_printk+0x113/0x1a0 lib/seq_buf.c:126
 mem_cgroup_print_oom_meminfo+0x169/0x250 mm/memcontrol.c:1615
 dump_header+0xa0/0x220 mm/oom_kill.c:469
 oom_kill_process+0x334/0x3f0 mm/oom_kill.c:1040
 out_of_memory+0x979/0xb80 mm/oom_kill.c:1178
 mem_cgroup_out_of_memory+0x13d/0x190 mm/memcontrol.c:1667
 mem_cgroup_oom mm/memcontrol.c:1690 [inline]
 try_charge_memcg+0x5e2/0x870 mm/memcontrol.c:2346
 try_charge mm/memcontrol.c:2446 [inline]
 charge_memcg+0x51/0xc0 mm/memcontrol.c:4592
 __mem_cgroup_charge+0x28/0xb0 mm/memcontrol.c:4609
 mem_cgroup_charge include/linux/memcontrol.h:642 [inline]
 shmem_alloc_and_add_folio mm/shmem.c:1903 [inline]
 shmem_get_folio_gfp+0x470/0xd40 mm/shmem.c:2533
 shmem_get_folio mm/shmem.c:2639 [inline]
 shmem_write_begin+0xa8/0x190 mm/shmem.c:3289
 generic_perform_write+0x181/0x490 mm/filemap.c:4103
 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3464
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x49d/0x8d0 fs/read_write.c:684
 ksys_pwrite64 fs/read_write.c:791 [inline]
 __do_sys_pwrite64 fs/read_write.c:799 [inline]
 __se_sys_pwrite64 fs/read_write.c:796 [inline]
 __x64_sys_pwrite64+0xfd/0x150 fs/read_write.c:796
 x64_sys_call+0xe45/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:19
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86876778 of 16 bytes by task 2994 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2185
 syslog_print+0x23a/0x540 kernel/printk/printk.c:1650
 do_syslog+0x52b/0x7e0 kernel/printk/printk.c:1785
 __do_sys_syslog kernel/printk/printk.c:1877 [inline]
 __se_sys_syslog kernel/printk/printk.c:1875 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1875
 x64_sys_call+0x2ea0/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 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: 2994 Comm: klogd Not tainted 6.15.0-rc6-syzkaller-00278-g172a9d94339c #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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