KCSAN: data-race in data_push_tail / number

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 894d6f401b21 Merge tag 'spi-fix-v5.14-rc4' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=150e0e04300000
kernel config: https://syzkaller.appspot.com/x/.config?x=325496b7f882bca
dashboard link: https://syzkaller.appspot.com/bug?extid=698615f208a1a0fa0ae6
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+698615...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in data_push_tail / number

write to 0xffffffff8414a2b4 of 1 bytes by task 21347 on cpu 1:
number+0x836/0xb50 lib/vsprintf.c:556
vsnprintf+0xb6d/0xed0 lib/vsprintf.c:2863
vscnprintf+0x29/0x80 lib/vsprintf.c:2900
printk_sprint kernel/printk/printk.c:2012 [inline]
vprintk_store+0x4c1/0x9c0 kernel/printk/printk.c:2115
vprintk_emit+0xca/0x3d0 kernel/printk/printk.c:2157
vprintk_default+0x22/0x30 kernel/printk/printk.c:2185
vprintk+0x15a/0x170 kernel/printk/printk_safe.c:392
printk+0x62/0x87 kernel/printk/printk.c:2216
set_capacity_and_notify+0x15a/0x1c0 block/genhd.c:66
loop_set_size drivers/block/loop.c:298 [inline]
loop_configure+0xc8e/0xeb0 drivers/block/loop.c:1295
lo_ioctl+0x59b/0x1340 drivers/block/loop.c:1847
blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:585
block_ioctl+0x6d/0x80 fs/block_dev.c:1604
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:1069 [inline]
__se_sys_ioctl+0xcb/0x140 fs/ioctl.c:1055
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:1055
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff8414a2b0 of 8 bytes by task 21349 on cpu 0:
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:2105
vprintk_emit+0xca/0x3d0 kernel/printk/printk.c:2157
vprintk_default+0x22/0x30 kernel/printk/printk.c:2185
vprintk+0x15a/0x170 kernel/printk/printk_safe.c:392
printk+0x62/0x87 kernel/printk/printk.c:2216
set_capacity_and_notify+0x15a/0x1c0 block/genhd.c:66
loop_set_size drivers/block/loop.c:298 [inline]
loop_configure+0xc8e/0xeb0 drivers/block/loop.c:1295
lo_ioctl+0x59b/0x1340 drivers/block/loop.c:1847
blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:585
block_ioctl+0x6d/0x80 fs/block_dev.c:1604
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:1069 [inline]
__se_sys_ioctl+0xcb/0x140 fs/ioctl.c:1055
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:1055
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000100006399 -> 0x0a3231323135206f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21349 Comm: syz-executor.4 Not tainted 5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

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