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Message-ID: <CAO6TR8Uhmzf17X4RH6zBy-oyacvGEhL4D3XfbhOOn5D-2Mv39Q@mail.gmail.com> Date: Fri, 15 Jan 2016 13:54:24 -0700 From: Jeff Merkey <linux.mdb@...il.com> To: Dmitry Vyukov <dvyukov@...gle.com> Cc: Gleb Natapov <gleb@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>, kvm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, syzkaller <syzkaller@...glegroups.com>, Kostya Serebryany <kcc@...gle.com>, Alexander Potapenko <glider@...gle.com>, Eric Dumazet <edumazet@...gle.com>, Sasha Levin <sasha.levin@...cle.com> Subject: Re: kvm: GPF in kvm_lapic_latched_init On 1/15/16, Dmitry Vyukov <dvyukov@...gle.com> wrote: > On Fri, Jan 15, 2016 at 8:59 PM, Jeff Merkey <linux.mdb@...il.com> wrote: >> On 1/8/16, Dmitry Vyukov <dvyukov@...gle.com> wrote: >>> Hello, >>> >>> The following program triggers GPF in kvm_lapic_latched_init if run in >>> a parallel loop: >>> https://gist.githubusercontent.com/dvyukov/524b398f379440b21115/raw/9627095f57a72501fb51bf7565471d31732beeee/gistfile1.txt >>> >>> kasan: GPF could be caused by NULL-ptr deref or user memory >>> accessgeneral protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN >>> Modules linked in: >>> CPU: 3 PID: 14426 Comm: a.out Not tainted 4.4.0-rc8+ #217 >>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs >>> 01/01/2011 >>> task: ffff880061099780 ti: ffff880062e30000 task.ti: ffff880062e30000 >>> RIP: 0010:[<ffffffff81057171>] [<ffffffff81057171>] >>> kvm_arch_vcpu_ioctl+0xa31/0x2ef0 >>> RSP: 0018:ffff880062e37900 EFLAGS: 00010206 >>> RAX: dffffc0000000000 RBX: 1ffff1000c5c6f25 RCX: 1ffff1000c41b7cb >>> RDX: 000000000000001e RSI: 000000008040ae9f RDI: 00000000000000f0 >>> RBP: ffff880062e37c10 R08: 0000000000000000 R09: 0000000000000000 >>> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 >>> R13: 0000000000000000 R14: ffff880062e37be8 R15: 0000000000000000 >>> FS: 00007f4aa815f700(0000) GS:ffff88006d700000(0000) >>> knlGS:0000000000000000 >>> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >>> CR2: 00007f4aa795de78 CR3: 00000000613c2000 CR4: 00000000000026e0 >>> Stack: >>> 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >>> 0000000020006fe4 0000000041b58ab3 ffffffff86e2e588 ffffffff81056740 >>> 0000000000000001 ffff880061099f60 0000000000000498 ffff880061099f68 >>> Call Trace: >>> [<ffffffff8101cb52>] kvm_vcpu_ioctl+0x1e2/0xd00 >>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:2526 >>> [< inline >] vfs_ioctl fs/ioctl.c:43 >>> [<ffffffff817b36b1>] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:607 >>> [< inline >] SYSC_ioctl fs/ioctl.c:622 >>> [<ffffffff817b3eff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 >>> [<ffffffff85e745b6>] entry_SYSCALL_64_fastpath+0x16/0x7a >>> arch/x86/entry/entry_64.S:185 >>> Code: 85 2d 20 00 00 4d 8b a4 24 60 03 00 00 e8 c8 8b 50 00 49 8d bc >>> 24 f0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> >>> 3c 02 00 0f 85 f3 1f 00 00 4d 8b a4 24 f0 00 00 00 41 83 e4 >>> RIP [< inline >] constant_test_bit >>> ./arch/x86/include/asm/bitops.h:311 >>> RIP [< inline >] kvm_lapic_latched_init >>> arch/x86/kvm/lapic.h:164 >>> RIP [< inline >] kvm_vcpu_ioctl_x86_get_vcpu_events >>> arch/x86/kvm/x86.c:2936 >>> RIP [<ffffffff81057171>] kvm_arch_vcpu_ioctl+0xa31/0x2ef0 >>> arch/x86/kvm/x86.c:3347 >>> RSP <ffff880062e37900> >>> ---[ end trace 16449377928e034b ]--- >>> >>> >>> or: >>> >>> kasan: GPF could be caused by NULL-ptr deref or user memory >>> accessgeneral protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN >>> Modules linked in: >>> CPU: 0 PID: 9555 Comm: syz-executor Not tainted 4.4.0-rc8+ #217 >>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs >>> 01/01/2011 >>> task: ffff88006301de00 ti: ffff880062568000 task.ti: ffff880062568000 >>> RIP: 0010:[<ffffffff810cf5ab>] [<ffffffff810cf5ab>] >>> wait_lapic_expire+0x6b/0x560 >>> RSP: 0018:ffff88006256fa48 EFLAGS: 00010006 >>> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff88006301e5c8 >>> RDX: 0000000000000011 RSI: 0000000000000000 RDI: ffff880033590360 >>> RBP: ffff88006256fa88 R08: 0000000000000001 R09: 0000000000000002 >>> R10: 0000000000000001 R11: 0000000000000001 R12: ffff880033590000 >>> R13: ffff880033590030 R14: 0000000000000088 R15: ffff88003359002c >>> FS: 00007f4809354700(0000) GS:ffff88003ec00000(0000) >>> knlGS:0000000000000000 >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> CR2: 00007f4808b53000 CR3: 0000000033f3f000 CR4: 00000000000026f0 >>> Stack: >>> ffff88006256fa70 0000000000000082 0000000000000003 ffff88006301de00 >>> ffff880033590030 ffff880033590030 ffff880033590000 ffff88003359002c >>> ffff88006256fc10 ffffffff8106a1dc ffffffff8106a75b 0000000000013210 >>> Call Trace: >>> [< inline >] vcpu_enter_guest arch/x86/kvm/x86.c:6523 >>> [< inline >] vcpu_run arch/x86/kvm/x86.c:6660 >>> [<ffffffff8106a1dc>] kvm_arch_vcpu_ioctl_run+0x25ec/0x5820 >>> arch/x86/kvm/x86.c:6818 >>> [<ffffffff8101cf61>] kvm_vcpu_ioctl+0x5f1/0xd00 >>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:2375 >>> [< inline >] vfs_ioctl fs/ioctl.c:43 >>> [<ffffffff817b36b1>] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:607 >>> [< inline >] SYSC_ioctl fs/ioctl.c:622 >>> [<ffffffff817b3eff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 >>> [<ffffffff85e745b6>] entry_SYSCALL_64_fastpath+0x16/0x7a >>> arch/x86/entry/entry_64.S:185 >>> Code: 60 03 00 00 0f 1f 44 00 00 e8 92 07 49 00 4c 8d b3 88 00 00 00 >>> e8 86 07 49 00 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> >>> 3c 02 00 0f 85 d8 04 00 00 4c 8b ab 88 00 00 00 4d 85 ed 75 >>> RIP [<ffffffff810cf5ab>] wait_lapic_expire+0x6b/0x560 >>> arch/x86/kvm/lapic.c:1245 >>> RSP <ffff88006256fa48> >>> ---[ end trace 560c2b85e36670bc ]--- >>> >>> or: >>> >>> kasan: GPF could be caused by NULL-ptr deref or user memory >>> accessgeneral protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN >>> Modules linked in: >>> CPU: 3 PID: 11264 Comm: syz-executor Not tainted 4.4.0-rc8+ #217 >>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs >>> 01/01/2011 >>> task: ffff880064d55e00 ti: ffff880064dc0000 task.ti: ffff880064dc0000 >>> RIP: 0010:[<ffffffff810d138d>] [<ffffffff810d138d>] >>> apic_has_pending_timer+0x7d/0x210 >>> RSP: 0018:ffff880064dc7a60 EFLAGS: 00010206 >>> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000004 >>> RDX: 0000000000000017 RSI: 0000000000000000 RDI: 00000000000000b8 >>> RBP: ffff880064dc7a70 R08: 0000000000000002 R09: 0000000000000001 >>> R10: ffff880064d55e00 R11: ffff880063528220 R12: ffff880063250030 >>> R13: ffff880063250030 R14: ffff880063250000 R15: 0000000000000000 >>> FS: 00007fb05f305700(0000) GS:ffff88006d700000(0000) >>> knlGS:0000000000000000 >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> CR2: 00000000006d7760 CR3: 0000000065ae9000 CR4: 00000000000026e0 >>> Stack: >>> ffff880063250000 ffff880063250030 ffff880064dc7a88 ffffffff810c7af5 >>> ffffffff86fee5c0 ffff880064dc7c10 ffffffff810685d4 ffffffff8106a75b >>> 0000000000013210 ffff880065a35000 1ffff1000c9b8f59 ffff880064dc0008 >>> Call Trace: >>> [<ffffffff810c7af5>] kvm_cpu_has_pending_timer+0x15/0x20 >>> arch/x86/kvm/irq.c:36 >>> [< inline >] vcpu_run arch/x86/kvm/x86.c:6669 >>> [<ffffffff810685d4>] kvm_arch_vcpu_ioctl_run+0x9e4/0x5820 >>> arch/x86/kvm/x86.c:6818 >>> [<ffffffff8101cf61>] kvm_vcpu_ioctl+0x5f1/0xd00 >>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:2375 >>> [< inline >] vfs_ioctl fs/ioctl.c:43 >>> [<ffffffff817b36b1>] do_vfs_ioctl+0x681/0xe40 fs/ioctl.c:607 >>> [< inline >] SYSC_ioctl fs/ioctl.c:622 >>> [<ffffffff817b3eff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 >>> [<ffffffff85e745b6>] entry_SYSCALL_64_fastpath+0x16/0x7a >>> arch/x86/entry/entry_64.S:185 >>> Code: ba e9 48 00 0f 1f 44 00 00 e8 b0 e9 48 00 e8 ab e9 48 00 48 8d >>> bb b8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> >>> 3c 02 00 0f 85 46 01 00 00 4c 8b a3 b8 00 00 00 48 b8 00 00 >>> RIP [< inline >] arch_static_branch >>> ./arch/x86/include/asm/jump_label.h:21 >>> RIP [< inline >] static_key_false >>> include/linux/jump_label.h:133 >>> RIP [< inline >] kvm_apic_hw_enabled arch/x86/kvm/lapic.h:117 >>> RIP [< inline >] apic_enabled arch/x86/kvm/lapic.c:121 >>> RIP [<ffffffff810d138d>] apic_has_pending_timer+0x7d/0x210 >>> arch/x86/kvm/lapic.c:1731 >>> RSP <ffff880064dc7a60> >>> ---[ end trace fe9c10b88e48c946 ]--- >>> >>> >>> All crashes suggest that apic is NULL. >>> >>> On commit b06f3a168cdcd80026276898fd1fee443ef25743 (Jan 6). >>> >> >> Dmitry, >> >> You need to check your test harness and add checks for which CPL the >> kernel is running at for these GPF faults and add that to your report. >> I realize that there are a lot of kernel subsystems which are coded >> very loose on checking for this stuff. I have looked through some of >> these hangs you reported and I think one of them is related to a >> swapgs instruction getting nested, and two others related to code >> touching hardware. >> >> Can you figure out how to send the info as to what privilege level you >> are at when these faults occur? This one looks like swapgs got nested >> and gs was pointing off to oblivion. > > > The program opens /dev/kvm under root because it is mounted as 700. > But then do ioctl's under user nobody. > Does it make sense to add UID to kernel BUG/WARNING (at least > capable(CAP_SYS_ADMIN) flag)? Because it's a pretty generic concern > for all crashes. > Well !!(cs & 3) is a good clue. According to CS (at least what this says) we are at ring 0 on this one with gs not set. Jeff
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