On Thu, Dec 14, 2023 at 10:39 PM 'Dave Chinner' via syzkaller-bugs <syzkaller-bugs@xxxxxxxxxxxxxxxx> wrote: > > On Thu, Dec 14, 2023 at 03:55:00PM +0100, Alexander Potapenko wrote: > > On Wed, Dec 13, 2023 at 10:58 PM 'Dave Chinner' via syzkaller-bugs > > <syzkaller-bugs@xxxxxxxxxxxxxxxx> wrote: > > > > > > On Thu, Dec 14, 2023 at 08:16:07AM +1100, Dave Chinner wrote: > > > > [cc linux-xfs@xxxxxxxxxxxxxxx because that's where all questions > > > > about XFS stuff should be directed, not to random individual > > > > developers. ] > > > > > > > > On Wed, Dec 13, 2023 at 11:49:50AM +0100, Alexander Potapenko wrote: > > > > > Hi Christoph, Dave, > > > > > > > > > > The repro provided by Xingwei indeed works. > > > > > > Can you please test the patch below? > > > > It fixed the problem for me, feel free to add: > > > > Tested-by: Alexander Potapenko <glider@xxxxxxxxxx> > > Thanks. > > > As for the time needed to detect the bug, note that kmemcheck was > > never used together with syzkaller, so it couldn't have the chance to > > find it. > > > > KMSAN found this bug in April > > (https://syzkaller.appspot.com/bug?extid=a6d6b8fffa294705dbd8), > > KMSAN has been used for quite a long time with syzbot, however, > and it's supposed to find these problems, too. Yet it's only been > finding this for 6 months? > > > only > > half a year after we started mounting XFS images on syzbot. > > Really? Where did you get that from? syzbot has been exercising XFS > filesystems since 2017 - the bug reports to the XFS list go back at > least that far. You are right, syzbot used to mount XFS way before 2022. On the other hand, last fall there were some major changes to the way syz_mount_image() works, so I am attributing the newly detected bugs to those changes. Unfortunately we don't have much insight into reasons behind syzkaller being able to trigger one bug or another: once a bug is found for the first time, the likelihood to trigger it again increases, but finding it initially might be tricky. I don't understand much how trivial is the repro at https://gist.github.com/xrivendell7/c7bb6ddde87a892818ed1ce206a429c4, but overall we are not drilling deep enough into XFS. https://storage.googleapis.com/syzbot-assets/8547e3dd1cca/ci-upstream-kmsan-gce-c7402612.html (ouch, 230Mb!) shows very limited coverage.
