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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id a6sm15660458pfn.1.2021.07.12.14.29.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jul 2021 14:29:04 -0700 (PDT) Date: Mon, 12 Jul 2021 21:29:00 +0000 From: Sean Christopherson To: Thomas Gleixner Cc: syzbot , akpm@linux-foundation.org, bp@alien8.de, hpa@zytor.com, jmattson@google.com, joro@8bytes.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mark.rutland@arm.com, masahiroy@kernel.org, mingo@redhat.com, pbonzini@redhat.com, peterz@infradead.org, rafael.j.wysocki@intel.com, rostedt@goodmis.org, sedat.dilek@gmail.com, syzkaller-bugs@googlegroups.com, vitor@massaru.org, vkuznets@redhat.com, wanpengli@tencent.com, will@kernel.org, x86@kernel.org Subject: Re: [syzbot] general protection fault in try_grab_compound_head Message-ID: References: <0000000000009e89e205c63dda94@google.com> <87fswpot3i.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87fswpot3i.ffs@nanos.tec.linutronix.de> Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=i86YDTFr; spf=pass (imf28.hostedemail.com: domain of seanjc@google.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=seanjc@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EAC7390000A3 X-Stat-Signature: b8udeyqgjososs6rjwz44nnracaorm7j X-HE-Tag: 1626125345-30419 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jul 08, 2021, Thomas Gleixner wrote: > On Sat, Jul 03 2021 at 13:24, syzbot wrote: > > syzbot has bisected this issue to: > > > > commit 997acaf6b4b59c6a9c259740312a69ea549cc684 > > Author: Mark Rutland > > Date: Mon Jan 11 15:37:07 2021 +0000 > > > > lockdep: report broken irq restoration > > That's the commit which makes the underlying problem visible: > > raw_local_irq_restore() called with IRQs enabled > > and is triggered by this call chain: > > kvm_wait arch/x86/kernel/kvm.c:860 [inline] > kvm_wait+0xc3/0xe0 arch/x86/kernel/kvm.c:837 And the bug in kvm_wait() was fixed by commit f4e61f0c9add ("x86/kvm: Fix broken irq restoration in kvm_wait"). The bisection is bad, syzbot happened into the kvm_wait() WARN and got distracted. The original #GP looks stable, if someone from mm land has bandwidth.