On Fri, Oct 25, 2024 at 05:20:52PM +0200, Jann Horn wrote: > On Fri, Oct 25, 2024 at 1:37 PM Lorenzo Stoakes > <lorenzo.stoakes@xxxxxxxxxx> wrote: > > On Fri, Oct 25, 2024 at 04:23:30AM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: c6d9e43954bf Merge 6.12-rc4 into usb-next > > > git tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing > > > console output: https://syzkaller.appspot.com/x/log.txt?x=139f225f980000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=4a2bb21f91d75c65 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=0ca979b86eaec7337a89 > > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179f225f980000 > > > > > > Downloadable assets: > > > disk image: https://storage.googleapis.com/syzbot-assets/3bf4a453ec2f/disk-c6d9e439.raw.xz > > > vmlinux: https://storage.googleapis.com/syzbot-assets/e4a2db2a5d95/vmlinux-c6d9e439.xz > > > kernel image: https://storage.googleapis.com/syzbot-assets/8eb8e481b288/bzImage-c6d9e439.xz > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+0ca979b86eaec7337a89@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > > Isn't this just the same thing as [0]? > > > > Again I think we're just happening to hit a stall in the unmap logic rather than > > this being an mm thing. > > > > We retried that one a few times and it didn't hit any mm code after the > > first time. > > Random side comment: It would be nice if the kernel was able to report > hangs in two steps; somehow scan and mark the stack in a first pass, > then wait another minute or so, then scan the stack again to see which > functions we haven't returned out of within that minute, or something > along those lines... Yeah that'd be nice! You'd get more information that way, though of course one stalled task might hold a lock another actually in theory unstalled task might need thus deadlocking it... :) But at least you'd see that, and the lock splat there helps obviously.
