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BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff860654a0 of 8 bytes by task 12562 on cpu 0:
 data_alloc+0x291/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 __ext4_error_inode+0x30b/0x400 fs/ext4/super.c:848
 ext4_map_blocks+0xc76/0xf50
 ext4_getblk+0x112/0x500 fs/ext4/inode.c:833
 ext4_bread+0x2c/0x110 fs/ext4/inode.c:889
 __ext4_read_dirblock+0x77/0x5b0 fs/ext4/namei.c:144
 dx_probe+0x69/0xc20 fs/ext4/namei.c:822
 ext4_dx_find_entry fs/ext4/namei.c:1789 [inline]
 __ext4_find_entry+0x35e/0x10a0 fs/ext4/namei.c:1635
 ext4_lookup_entry fs/ext4/namei.c:1770 [inline]
 ext4_lookup+0xba/0x390 fs/ext4/namei.c:1838
 __lookup_slow+0x184/0x250 fs/namei.c:1692
 lookup_slow+0x3c/0x60 fs/namei.c:1709
 walk_component fs/namei.c:2004 [inline]
 link_path_walk+0x621/0x810 fs/namei.c:2331
 path_lookupat+0x72/0x2b0 fs/namei.c:2492
 do_o_path+0x44/0x120 fs/namei.c:3784
 path_openat+0x1c85/0x1fa0 fs/namei.c:3806
 do_filp_open+0xf7/0x200 fs/namei.c:3840
 do_sys_openat2+0xab/0x120 fs/open.c:1413
 do_sys_open fs/open.c:1428 [inline]
 __do_sys_openat fs/open.c:1444 [inline]
 __se_sys_openat fs/open.c:1439 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1439
 x64_sys_call+0x1057/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff860654a0 of 8 bytes by task 12250 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+0x235/0xb60 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2269
 vprintk_emit+0x10c/0x5e0 kernel/printk/printk.c:2329
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2363
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:45
 _printk+0x7a/0xa0 kernel/printk/printk.c:2373
 __ext4_msg+0x18e/0x1a0 fs/ext4/super.c:990
 ext4_put_super+0x91/0x7e0 fs/ext4/super.c:1295
 generic_shutdown_super+0xde/0x210 fs/super.c:642
 kill_block_super+0x2a/0x70 fs/super.c:1685
 ext4_kill_sb+0x44/0x80 fs/ext4/super.c:7301
 deactivate_locked_super+0x7d/0x1c0 fs/super.c:473
 deactivate_super+0x9f/0xb0 fs/super.c:506
 cleanup_mnt+0x268/0x2e0 fs/namespace.c:1267
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1274
 task_work_run+0x13a/0x1a0 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xbe/0x130 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffffc7088 -> 0x0000000000072c30

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12250 Comm: syz-executor Not tainted 6.10.0-rc7-syzkaller-00139-g8a18fda0febb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
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EXT4-fs (loop1): unmounting filesystem 00000000-0000-0000-0000-000000000000.