Re: [syzbot] KFENCE: use-after-free in kvm_fastop_exception
From: Matthieu Baerts <hidden>
Date: 2021-08-18 08:22:02
Also in:
linux-bluetooth, linux-fsdevel, lkml
Hi Pavel, On 18/08/2021 10:12, Pavel Skripkin wrote:
On 8/18/21 11:02 AM, Matthieu Baerts wrote:quoted
Hello, On 18/08/2021 00:21, syzbot wrote:quoted
syzbot has bisected this issue to: commit c4512c63b1193c73b3f09c598a6d0a7f88da1dd8 Author: Matthieu Baerts [off-list ref] Date: Fri Jun 25 21:25:22 2021 +0000 mptcp: fix 'masking a bool' warning bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=122b0655300000 start commit: b9011c7e671d Add linux-next specific files for 20210816 git tree: linux-next final oops: https://syzkaller.appspot.com/x/report.txt?x=112b0655300000 console output: https://syzkaller.appspot.com/x/log.txt?x=162b0655300000 kernel config: https://syzkaller.appspot.com/x/.config?x=a245d1aa4f055cc1 dashboard link: https://syzkaller.appspot.com/bug?extid=7b938780d5deeaaf938f syz repro: https://syzkaller.appspot.com/x/repro.syz?x=157a41ee300000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14f78ff9300000I'm pretty sure the commit c4512c63b119 ("mptcp: fix 'masking a bool' warning") doesn't introduce the reported bug. This minor fix is specific to MPTCP which doesn't seem to be used here. I'm not sure how I can tell syzbot this is a false positive.looks like it's fs/namei bug. Similar reports: https://syzkaller.appspot.com/bug?id=517fa734b92b7db404c409b924cf5c997640e324 https://syzkaller.appspot.com/bug?id=484483daf3652b40dae18531923aa9175d392a4d
Thank you for having checked! Should we mark them as "#syz dup" if you think they have the same root cause?
It's not false positive. I've suggested the fix here: https://groups.google.com/g/syzkaller-bugs/c/HE3c2fP5nic/m/1Yk17GBeAwAJ I am waiting for author comments about the fix :) But, yes, syzbot bisection is often wrong, so don't rely on it much :)
Yes sorry, I wanted to say the bisection picked a wrong commit :) All good then if syzbot often blames the wrong modification :) Cheers, Matt -- Tessares | Belgium | Hybrid Access Solutions www.tessares.net