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BUG: KCSAN: data-race in memchr / number

write to 0xffffffff883e0a83 of 1 bytes by task 19967 on cpu 0:
 number+0x7d0/0xa90 lib/vsprintf.c:564
 vsnprintf+0xa44/0xe30 lib/vsprintf.c:2890
 vscnprintf+0x42/0x90 lib/vsprintf.c:2930
 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2165
 vprintk_store+0x570/0x810 kernel/printk/printk.c:2279
 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
 blk_add_partition block/partitions/core.c:541 [inline]
 blk_add_partitions block/partitions/core.c:626 [inline]
 bdev_disk_changed+0x888/0xbe0 block/partitions/core.c:686
 loop_reread_partitions drivers/block/loop.c:514 [inline]
 loop_set_status+0x4ab/0x550 drivers/block/loop.c:1316
 lo_ioctl+0x892/0x1330
 blkdev_ioctl+0x37f/0x470 block/ioctl.c:642
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl+0xd3/0x150 fs/ioctl.c:890
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:890
 x64_sys_call+0x155d/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff883e0a83 of 1 bytes by task 19975 on cpu 1:
 memchr+0x2a/0x50 lib/string.c:791
 count_lines kernel/printk/printk_ringbuffer.c:1797 [inline]
 copy_data kernel/printk/printk_ringbuffer.c:1843 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1936 [inline]
 _prb_read_valid+0xa26/0xba0 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid_info+0x67/0x90 kernel/printk/printk_ringbuffer.c:2216
 find_first_fitting_seq+0x8a/0x310 kernel/printk/printk.c:1519
 syslog_print_all+0x11d/0x5a0 kernel/printk/printk.c:1670
 do_syslog+0x41c/0x7d0 kernel/printk/printk.c:1748
 __do_sys_syslog kernel/printk/printk.c:1826 [inline]
 __se_sys_syslog kernel/printk/printk.c:1824 [inline]
 __x64_sys_syslog+0x43/0x50 kernel/printk/printk.c:1824
 x64_sys_call+0x2695/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x69 -> 0x73

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19975 Comm: syz-executor.2 Not tainted 6.9.0-rc5-syzkaller-00042-ge88c4cfcb7b8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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