On Fri, Oct 25, 2024 at 11:13:33AM -0400, Alan Stern wrote: > On Fri, Oct 25, 2024 at 12:37:36PM +0100, Lorenzo Stoakes 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. > > > > Greg mentioned there was some weirdness with the dummy usb hcd controller > > in [1]. > > For what it's worth, that weirdness has been fixed in 6.12-rc4 by commit > 5189df7b8088 ("USB: gadget: dummy-hcd: Fix "task hung" problem"). Hm, but this is pointing at a commit that should have that? Strange. I do wonder if the fact CONFIG_DEBUG_VM_MAPLE_TREE is enabled (and by the way in the mm- stack cited) is a factor here, because that is a very very significant slowdown anyway. And I wonder whether it might be a good idea for syzbot to not set that flag when doing known-time-consuming things, or at least should up the RCU stall limits? > > Alan Stern
