linux-kernel - Re: [v5.15] WARNING in kvm_arch_vcpu_ioctl

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Message-ID: <ZOy5L4WCiy1hsiu0@google.com>
Date:   Mon, 28 Aug 2023 08:11:43 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc:     syzbot <syzbot+412c9ae97b4338c5187e@...kaller.appspotmail.com>,
        syzkaller-lts-bugs@...glegroups.com,
        syzbot <syzbot+b000b7d21f93fc69de32@...kaller.appspotmail.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org
Subject: Re: [v5.15] WARNING in kvm_arch_vcpu_ioctl_run

On Mon, Aug 28, 2023, Muhammad Usama Anjum wrote:
> On 5/5/23 1:28 PM, syzbot wrote:
> > syzbot has found a reproducer for the following issue on:
> > 
> > HEAD commit: 8a7f2a5c5aa1 Linux 5.15.110
> This same warning has also been found on  6.1.21.
> 
> > git tree: linux-5.15.y
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15f12318280000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=ba8d5c9d6c5289f
> > dashboard link: https://syzkaller.appspot.com/bug?extid=412c9ae97b4338c5187e
> > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e13c84280000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=149d9470280000
> I've tried all the C and syz reproducers. I've also tried syz-crash which
> launched multiple instances of VMs and ran syz reproducer. But the issue
> didn't get reproduced.
> 
> I don't have kvm skills. Can someone have a look at the the warning
> (probably by static analysis)?
> 
> > 
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/fc04f54c047f/disk-8a7f2a5c.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/6b4ba4cb1191/vmlinux-8a7f2a5c.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/d927dc3f9670/bzImage-8a7f2a5c.xz
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+412c9ae97b4338c5187e@...kaller.appspotmail.com
> > 
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 3502 at arch/x86/kvm/x86.c:10310 kvm_arch_vcpu_ioctl_run+0x1d63/0x1f80

"Fixed" by https://lore.kernel.org/all/20230808232057.2498287-1-seanjc@google.com,
in quotes because sadly the fix was to simply delete the sanity check :-(