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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff868ea798 of 88 bytes by task 3485 on cpu 0:
 prb_reserve+0x696/0xaf0 kernel/printk/printk_ringbuffer.c:1635
 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
 blk_add_partition block/partitions/core.c:540 [inline]
 blk_add_partitions block/partitions/core.c:633 [inline]
 bdev_disk_changed+0x821/0xcb0 block/partitions/core.c:693
 blkdev_get_whole+0x1f5/0x2d0 block/bdev.c:748
 bdev_open+0x280/0x7e0 block/bdev.c:957
 blkdev_open+0x259/0x290 block/fops.c:676
 do_dentry_open+0x649/0xa20 fs/open.c:964
 vfs_open+0x37/0x1e0 fs/open.c:1094
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1c5e/0x2170 fs/namei.c:4046
 do_filp_open+0x109/0x230 fs/namei.c:4073
 do_sys_openat2+0xa6/0x110 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1463
 x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
 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

read to 0xffffffff868ea798 of 8 bytes by task 2997 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1c4/0x920 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+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002ec3 -> 0x0000000000004ec3

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2997 Comm: klogd Not tainted 6.15.0-syzkaller-02245-gdd3922cf9d4d #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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