BUG: KCSAN: data-race in data_push_tail / number

write to 0xffffffff845086db of 1 bytes by task 22707 on cpu 0:
 number+0x836/0xb50 lib/vsprintf.c:529
 vsnprintf+0xb6d/0xed0 lib/vsprintf.c:2717
 va_format lib/vsprintf.c:1663 [inline]
 pointer+0xeb/0x800 lib/vsprintf.c:2283
 vsnprintf+0x8a1/0xed0 lib/vsprintf.c:2655
 vscnprintf+0x29/0x80 lib/vsprintf.c:2754
 printk_sprint kernel/printk/printk.c:1936 [inline]
 vprintk_store+0x4c1/0x9c0 kernel/printk/printk.c:2039
 vprintk_emit+0xca/0x3d0 kernel/printk/printk.c:2081
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2115
 vprintk_func+0x137/0x140 kernel/printk/printk_safe.c:401
 printk+0x62/0x82 kernel/printk/printk.c:2146
 __ext4_msg+0x103/0x110 fs/ext4/super.c:906
 ext4_fill_super+0x13ba/0x7f90 fs/ext4/super.c:4224
 mount_bdev+0x1e8/0x290 fs/super.c:1367
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6605
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4a/0x1a0 fs/super.c:1497
 do_new_mount fs/namespace.c:2903 [inline]
 path_mount+0x11d6/0x1ce0 fs/namespace.c:3233
 do_mount fs/namespace.c:3246 [inline]
 __do_sys_mount fs/namespace.c:3454 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3431
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3431
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff845086d8 of 8 bytes by task 22713 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:587 [inline]
 data_push_tail+0x125/0x460 kernel/printk/printk_ringbuffer.c:672
 data_alloc+0xbc/0x2b0 kernel/printk/printk_ringbuffer.c:1043
 prb_reserve+0x8f0/0xbc0 kernel/printk/printk_ringbuffer.c:1549
 vprintk_store+0x3e9/0x9c0 kernel/printk/printk.c:2029
 vprintk_emit+0xca/0x3d0 kernel/printk/printk.c:2081
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2115
 vprintk_func+0x137/0x140 kernel/printk/printk_safe.c:401
 printk+0x62/0x82 kernel/printk/printk.c:2146
 __ext4_msg+0x103/0x110 fs/ext4/super.c:906
 ext4_check_descriptors fs/ext4/super.c:2948 [inline]
 ext4_fill_super+0x4153/0x7f90 fs/ext4/super.c:4701
 mount_bdev+0x1e8/0x290 fs/super.c:1367
 ext4_mount+0x2d/0x40 fs/ext4/super.c:6605
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4a/0x1a0 fs/super.c:1497
 do_new_mount fs/namespace.c:2903 [inline]
 path_mount+0x11d6/0x1ce0 fs/namespace.c:3233
 do_mount fs/namespace.c:3246 [inline]
 __do_sys_mount fs/namespace.c:3454 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3431
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3431
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22713 Comm: syz-executor.5 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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