Re: [syzbot] [maple-tree?] BUG: unable to handle kernel paging request in mas_walk

Liam R. Howlett
2024-06-13T19:02:30Z

* Liam R. Howlett <Liam.Howlett@oracle.com> [240604 14:08]:
> * syzbot <syzbot+c67d06ab25a9bc4adf35@syzkaller.appspotmail.com> [240603 22:23]:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 4a4be1ad3a6e Revert "vfs: Delete the associated dentry whe..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=128638ba980000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=bd6024aedb15e15c
> > dashboard link: https://syzkaller.appspot.com/bug?extid=c67d06ab25a9bc4adf35
> > compiler: aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > userspace arch: arm64
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=106f71aa980000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b4ffc6980000
> >
> > Downloadable assets:
> > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/384ffdcca292/non_bootable_disk-4a4be1ad.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/75957361122b/vmlinux-4a4be1ad.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/6c766b0ec377/Image-4a4be1ad.gz.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+c67d06ab25a9bc4adf35@syzkaller.appspotmail.com
> >
> > Unable to handle kernel paging request at virtual address 00700000077b9b78
>
> I don't think the bot is testing my forced update of the tree, so I'll
> try again.
>
> #sys test git://git.infradead.org/users/jedix/linux-maple.git syz_20240603_v2
>
> This is a revert a some patches - which seems to stop all the crashing
> for me.
>
> Looks to be the same as this [1] syzbot report. All seem to be related
> to madvise and these patches are the last to modify the area (besides
> mseal() specifically calling out madvise, but that would not cause the
> issue).
>
> The patches I revered also name arm64 as special.
>
> [1] https://syzkaller.appspot.com/bug?extid=7eaa0d7b9fccf21052f1

This should be fixed in 6.10-rc3 because of the arm fix in the area I
suspected. I have no way of verifying that since the bot decided to
stop responding.

This puts us in a difficult situation of needing to jump on bot bugs for
security concerns and wasting copious amounts of time chasing our own
tails.