On 9/13/23 12:29, syzbot wrote:
Hello, syzbot found the following issue on: HEAD commit: f97e18a3f2fb Merge tag 'gpio-updates-for-v6.6' of git://gi.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12864667a80000 kernel config: https://syzkaller.appspot.com/x/.config?x=fe440f256d065d3b dashboard link: https://syzkaller.appspot.com/bug?extid=a36975231499dc24df44 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/b1781aaff038/disk-f97e18a3.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/5b915468fd6d/vmlinux-f97e18a3.xz kernel image: https://storage.googleapis.com/syzbot-assets/abc8ece931f3/bzImage-f97e18a3.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+a36975231499dc24df44@xxxxxxxxxxxxxxxxxxxxxxxxx ================================================================== BUG: KCSAN: data-race in io_wq_activate_free_worker / io_wq_worker_running write to 0xffff888127f736c4 of 4 bytes by task 4731 on cpu 1: io_wq_worker_running+0x64/0xa0 io_uring/io-wq.c:668 schedule_timeout+0xcc/0x230 kernel/time/timer.c:2167 io_wq_worker+0x4b2/0x840 io_uring/io-wq.c:633 ret_from_fork+0x2e/0x40 arch/x86/kernel/process.c:145 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 read to 0xffff888127f736c4 of 4 bytes by task 4719 on cpu 0: io_wq_get_acct io_uring/io-wq.c:168 [inline] io_wq_activate_free_worker+0xfa/0x280 io_uring/io-wq.c:267 io_wq_enqueue+0x262/0x450 io_uring/io-wq.c:914
1) the worst case scenario we'll choose a wrong type of worker, which is inconsequential. 2) we're changing the IO_WORKER_F_RUNNING bit, but checking for IO_WORKER_F_BOUND. The latter one is set at the very beginning, it would require compiler to be super inventive to actually hit the problem. I don't believe it's a problem, but it'll nice to attribute it properly, READ_ONCE?, or split IO_WORKER_F_BOUND out into a separate field.
io_queue_iowq+0x1d1/0x310 io_uring/io_uring.c:514 io_queue_sqe_fallback+0x82/0xe0 io_uring/io_uring.c:2084 io_submit_sqe io_uring/io_uring.c:2305 [inline] io_submit_sqes+0xbd3/0xfb0 io_uring/io_uring.c:2420 __do_sys_io_uring_enter io_uring/io_uring.c:3628 [inline] __se_sys_io_uring_enter+0x1f8/0x1c10 io_uring/io_uring.c:3562 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3562 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0x0000000d -> 0x0000000b Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 4719 Comm: syz-executor.1 Not tainted 6.5.0-syzkaller-01810-gf97e18a3f2fb #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023 ================================================================== --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the bug is already fixed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite bug's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the bug is a duplicate of another bug, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
-- Pavel Begunkov
