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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id mm11-20020a17090b358b00b0020d24ea4400sm1899772pjb.38.2022.11.04.10.39.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Nov 2022 10:39:34 -0700 (PDT) Date: Fri, 4 Nov 2022 17:39:31 +0000 From: Sean Christopherson To: Dmitry Vyukov Cc: syzbot , bp@alien8.de, brgerst@gmail.com, dave.hansen@linux.intel.com, hpa@zytor.com, kirill@shutemov.name, linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, thomas.lendacky@amd.com, x86@kernel.org Subject: Re: [syzbot] BUG: unable to handle kernel paging request in get_desc Message-ID: References: <00000000000035fba305eca64106@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 04, 2022, Sean Christopherson wrote: > On Fri, Nov 04, 2022, Dmitry Vyukov wrote: > > On Fri, 4 Nov 2022 at 08:28, 'Sean Christopherson' via syzkaller-bugs > > wrote: > > > > > > On Fri, Nov 04, 2022, syzbot wrote: > > > > Hello, > > > > > > > > syzbot found the following issue on: > > > > > > > > HEAD commit: 81214a573d19 Add linux-next specific files for 20221103 > > > > git tree: linux-next > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=132019de880000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=cdc625e9234bac0 > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=ffb4f000dc2872c93f62 > > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12dd52ca880000 > > > > > > > > Downloadable assets: > > > > disk image: https://storage.googleapis.com/syzbot-assets/5d4dda497754/disk-81214a57.raw.xz > > > > vmlinux: https://storage.googleapis.com/syzbot-assets/9658efff160a/vmlinux-81214a57.xz > > > > kernel image: https://storage.googleapis.com/syzbot-assets/3711180f2565/bzImage-81214a57.xz > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > > Reported-by: syzbot+ffb4f000dc2872c93f62@syzkaller.appspotmail.com > > > > > > > > BUG: unable to handle page fault for address: fffffbc5a1c22e00 > > > > #PF: supervisor read access in kernel mode > > > > #PF: error_code(0x0000) - not-present page > > > > PGD 23ffe4067 P4D 23ffe4067 PUD 13ff2d067 PMD 13ff2c067 PTE 0 > > > > Oops: 0000 [#1] PREEMPT SMP KASAN > > > > CPU: 0 PID: 5368 Comm: syz-executor.2 Not tainted 6.1.0-rc3-next-20221103-syzkaller #0 > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 > > > > RIP: 0010:get_desc+0x128/0x460 arch/x86/lib/insn-eval.c:660 > > > > > > I'm pretty sure this is the same thing as > > > > > > BUG: unable to handle kernel paging request in vmx_handle_exit_irqoff > > > > > > I'll verify and get a patch posted shortly. > > > > This repro does not create any VMs, it's just: > > > > iopl(0x3) > > rt_sigreturn() > > > > Do you still think it's related to the vmx_handle_exit_irqoff issue? > > Yes, the issue is that the shadow for the read-only IDT mapping in the CPU entry > area isn't populated (commit 9fd429c28073 ("x86/kasan: Map shadow for percpu pages > on demand") is to blame). The bug manifests anytime software manually does an IDT > lookup. Hrm, but the lookup is into the GDT, not the IDT, and I haven't been able to reproduce this one. I'll leave it open for now.