[moderation] [scsi?] KCSAN: data-race in sg_open / sg_release (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 39f90c196721 Merge tag 'for_linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1091def0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=86a2212b48ce4ce2
dashboard link: https://syzkaller.appspot.com/bug?extid=92b6af4f2ee6b9e092dc
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [James.B...@HansenPartnership.com dgil...@interlog.com linux-...@vger.kernel.org linux...@vger.kernel.org martin....@oracle.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d7e6adef211e/disk-39f90c19.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b91130e58c7a/vmlinux-39f90c19.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cf89a7b36b34/bzImage-39f90c19.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+92b6af...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in sg_open / sg_release

read-write to 0xffff8881019375a8 of 4 bytes by task 20198 on cpu 1:
sg_release+0x5b/0x260 drivers/scsi/sg.c:389
__fput+0x298/0x650 fs/file_table.c:468
____fput+0x1c/0x30 fs/file_table.c:496
task_work_run+0x131/0x1a0 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xe4/0x100 kernel/entry/common.c:43
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881019375a8 of 4 bytes by task 20199 on cpu 0:
open_wait drivers/scsi/sg.c:253 [inline]
sg_open+0x550/0xc70 drivers/scsi/sg.c:334
chrdev_open+0x2eb/0x3a0 fs/char_dev.c:414
do_dentry_open+0x646/0xa20 fs/open.c:965
vfs_open+0x37/0x1e0 fs/open.c:1095
do_open fs/namei.c:3887 [inline]
path_openat+0x1c5e/0x2170 fs/namei.c:4046
do_filp_open+0x109/0x230 fs/namei.c:4073
do_sys_openat2+0xa6/0x110 fs/open.c:1435
do_sys_open fs/open.c:1450 [inline]
__do_sys_openat fs/open.c:1466 [inline]
__se_sys_openat fs/open.c:1461 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1461
x64_sys_call+0x2e9c/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20199 Comm: syz.1.5018 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
==================================================================


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[syzbot]

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