[moderation] [block?] KCSAN: data-race in bdev_set_nr_sectors / guard_bio_eod

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e42b1a9a2557 Merge tag 'spi-fix-v6.12-rc5' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14cff0e7980000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b957b77e265904d
dashboard link: https://syzkaller.appspot.com/bug?extid=fdd52d81423152c1a318
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/9ffa8ca23b00/disk-e42b1a9a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/07044391294a/vmlinux-e42b1a9a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/177b8fada5be/bzImage-e42b1a9a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fdd52d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in bdev_set_nr_sectors / guard_bio_eod

write to 0xffff8881004c1908 of 8 bytes by task 7883 on cpu 1:
bdev_set_nr_sectors+0x45/0x60 block/bdev.c:450
set_capacity block/genhd.c:61 [inline]
set_capacity_and_notify+0x6e/0x160 block/genhd.c:74
loop_set_size drivers/block/loop.c:232 [inline]
loop_set_status+0x399/0x540 drivers/block/loop.c:1286
lo_ioctl+0x7f1/0x11c0
blkdev_ioctl+0x359/0x450 block/ioctl.c:693
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xcd/0x140 fs/ioctl.c:893
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
x64_sys_call+0x15cc/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:17
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 0xffff8881004c1908 of 8 bytes by task 7891 on cpu 0:
bdev_nr_sectors include/linux/blkdev.h:784 [inline]
guard_bio_eod+0x29/0xb0 block/bio.c:694
submit_bh_wbc+0x25f/0x320 fs/buffer.c:2812
submit_bh+0x1e/0x30 fs/buffer.c:2824
__ext4_read_bh fs/ext4/super.c:175 [inline]
ext4_read_bh_nowait fs/ext4/super.c:187 [inline]
ext4_sb_breadahead_unmovable+0x169/0x190 fs/ext4/super.c:269
__ext4_get_inode_loc+0x6d4/0x910 fs/ext4/inode.c:4491
ext4_get_inode_loc+0x65/0xe0 fs/ext4/inode.c:4536
ext4_read_inline_link+0x47/0x290 fs/ext4/inline.c:1588
ext4_get_link+0x85/0x2b0 fs/ext4/symlink.c:87
pick_link+0x43f/0x7e0
step_into+0x725/0x810 fs/namei.c:1923
open_last_lookups fs/namei.c:3721 [inline]
path_openat+0x1234/0x1fa0 fs/namei.c:3930
do_filp_open+0xf7/0x200 fs/namei.c:3960
do_sys_openat2+0xab/0x120 fs/open.c:1415
do_sys_open fs/open.c:1430 [inline]
__do_sys_creat fs/open.c:1508 [inline]
__se_sys_creat fs/open.c:1502 [inline]
__x64_sys_creat+0x66/0x90 fs/open.c:1502
x64_sys_call+0x2cbf/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:86
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

value changed: 0x0000000000000800 -> 0x00000000000007ff

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7891 Comm: syz.3.1624 Not tainted 6.12.0-rc5-syzkaller-00005-ge42b1a9a2557 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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