On Thu, 12 Sept 2024 at 13:03, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: > > On Thu, Sep 12, 2024 at 01:11:21AM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 7c6a3a65ace7 minmax: reduce min/max macro expansion in ato.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=1608e49f980000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=1e7d02549be622b2 > > dashboard link: https://syzkaller.appspot.com/bug?extid=8a02104389c2e0ef5049 > > 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/a1f7496fa21f/disk-7c6a3a65.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/f423739e51a9/vmlinux-7c6a3a65.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/b65a0f38cbd7/bzImage-7c6a3a65.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+8a02104389c2e0ef5049@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KCSAN: data-race in virtqueue_disable_cb / vring_interrupt > > > > write to 0xffff88810285ef52 of 1 bytes by interrupt on cpu 0: > > vring_interrupt+0x12b/0x180 drivers/virtio/virtio_ring.c:2591 > > > Yes, it's racy! > > 2589: /* Just a hint for performance: so it's ok that this can be racy! */ > 2590: if (vq->event) > 2591: vq->event_triggered = true; > > > Question: is there a way to annotate code to tell syzbot it's ok? In this case, "if (data_race(vq->event))" might be the right choice. This is a quick guide on which access primitive to use in concurrent code: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/memory-model/Documentation/access-marking.txt Thanks, -- Marco
