[moderation] [block?] KCSAN: data-race in memchr / number (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e88c4cfcb7b8 Merge tag 'for-6.9-rc5-tag' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1530eccf180000
kernel config: https://syzkaller.appspot.com/x/.config?x=4128b708dfac799b
dashboard link: https://syzkaller.appspot.com/bug?extid=8da930cfea359c5c1ba2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/06508e2c52b4/disk-e88c4cfc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f4362fce12b5/vmlinux-e88c4cfc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/93228f45c53c/bzImage-e88c4cfc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8da930...@syzkaller.appspotmail.com

==================================================================
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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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.