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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ac3fd01e4c1e Linux 6.18-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15446e92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=655255e3ef31c19b
dashboard link: https://syzkaller.appspot.com/bug?extid=61273e29fc4ceb197b73
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
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/0b87e3335067/disk-ac3fd01e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5d86405bc71d/vmlinux-ac3fd01e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5cdf269de51b/bzImage-ac3fd01e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+61273e...@syzkaller.appspotmail.com

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

read-write to 0xffff8881026ae2a8 of 4 bytes by task 22050 on cpu 0:
sg_open+0xb8e/0xc70 drivers/scsi/sg.c:355
chrdev_open+0x2eb/0x3a0 fs/char_dev.c:414
do_dentry_open+0x649/0xa20 fs/open.c:965
vfs_open+0x37/0x1e0 fs/open.c:1097
do_open fs/namei.c:3975 [inline]
path_openat+0x1c5e/0x2170 fs/namei.c:4134
do_filp_open+0x109/0x230 fs/namei.c:4161
do_sys_openat2+0xa6/0x110 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1463
x64_sys_call+0x2eab/0x3000 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

read to 0xffff8881026ae2a8 of 4 bytes by task 22026 on cpu 1:
open_wait drivers/scsi/sg.c:253 [inline]
sg_open+0x608/0xc70 drivers/scsi/sg.c:334
chrdev_open+0x2eb/0x3a0 fs/char_dev.c:414
do_dentry_open+0x649/0xa20 fs/open.c:965
vfs_open+0x37/0x1e0 fs/open.c:1097
do_open fs/namei.c:3975 [inline]
path_openat+0x1c5e/0x2170 fs/namei.c:4134
do_filp_open+0x109/0x230 fs/namei.c:4161
do_sys_openat2+0xa6/0x110 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1463
x64_sys_call+0x2eab/0x3000 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: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22026 Comm: syz.6.6227 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================


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