Konrad Rzeszutek Wilk
2020-Aug-24 15:06 UTC
Is: virtio_gpu_object_shmem_init issues? Was:Re: upstream boot error: general protection fault in swiotlb_map
On Thu, Aug 06, 2020 at 03:46:23AM -0700, syzbot wrote:> Hello, > > syzbot found the following issue on: > > HEAD commit: 47ec5303 Merge git://git.kernel.org/pub/scm/linux/kernel/g.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=16fe1dea900000 > kernel config: https://syzkaller.appspot.com/x/.config?x=7c06047f622c5724 > dashboard link: https://syzkaller.appspot.com/bug?extid=3f86afd0b1e4bf1cb64c > compiler: gcc (GCC) 10.1.0-syz 20200507 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+3f86afd0b1e4bf1cb64c at syzkaller.appspotmail.com > > ceph: loaded (mds proto 32) > NET: Registered protocol family 38 > async_tx: api initialized (async) > Key type asymmetric registered > Asymmetric key parser 'x509' registered > Asymmetric key parser 'pkcs8' registered > Key type pkcs7_test registered > Asymmetric key parser 'tpm_parser' registered > Block layer SCSI generic (bsg) driver version 0.4 loaded (major 243) > io scheduler mq-deadline registered > io scheduler kyber registered > io scheduler bfq registered > hgafb: HGA card not detected. > hgafb: probe of hgafb.0 failed with error -22 > usbcore: registered new interface driver udlfb > uvesafb: failed to execute /sbin/v86d > uvesafb: make sure that the v86d helper is installed and executable > uvesafb: Getting VBE info block failed (eax=0x4f00, err=-2) > uvesafb: vbe_init() failed with -22 > uvesafb: probe of uvesafb.0 failed with error -22 > vga16fb: mapped to 0x000000008aac772d > Console: switching to colour frame buffer device 80x30 > fb0: VGA16 VGA frame buffer device > input: Power Button as /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0 > ACPI: Power Button [PWRF] > ioatdma: Intel(R) QuickData Technology Driver 5.00 > PCI Interrupt Link [GSIF] enabled at IRQ 21 > PCI Interrupt Link [GSIG] enabled at IRQ 22 > PCI Interrupt Link [GSIH] enabled at IRQ 23 > N_HDLC line discipline registered with maxframe=4096 > Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled > 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A > Cyclades driver 2.6 > Initializing Nozomi driver 2.1d > RocketPort device driver module, version 2.09, 12-June-2003 > No rocketport ports found; unloading driver > Non-volatile memory driver v1.3 > Linux agpgart interface v0.103 > [drm] Initialized vgem 1.0.0 20120112 for vgem on minor 0 > [drm] Initialized vkms 1.0.0 20180514 for vkms on minor 1 > usbcore: registered new interface driver udl > [drm] pci: virtio-vga detected at 0000:00:01.0 > fb0: switching to virtiodrmfb from VGA16 VGA > Console: switching to colour VGA+ 80x25 > virtio-pci 0000:00:01.0: vgaarb: deactivate vga console > Console: switching to colour dummy device 80x25 > [drm] features: -virgl +edid > [drm] number of scanouts: 1 > [drm] number of cap sets: 0 > [drm] Initialized virtio_gpu 0.1.0 0 for virtio0 on minor 2 > general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.8.0-syzkaller #0 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 > RIP: 0010:swiotlb_map+0x5ac/0x700 kernel/dma/swiotlb.c:683 > Code: 28 04 00 00 48 c1 ea 03 80 3c 02 00 0f 85 4d 01 00 00 4c 8b a5 18 04 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 01 00 00 48 8d 7d 50 4d 8b 24 24 48 b8 00 00 > RSP: 0000:ffffc9000034f3e0 EFLAGS: 00010246 > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8162cc1d > RDX: 0000000000000000 RSI: ffffffff8162cc98 RDI: ffff88802971a470 > RBP: ffff88802971a048 R08: 0000000000000001 R09: ffffffff8c5dba77 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 000000007ac00000 R14: dffffc0000000000 R15: 0000000000001000 > FS: 0000000000000000(0000) GS:ffff88802ce00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00000000ffffffff CR3: 0000000009a8d000 CR4: 0000000000350ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > dma_direct_map_page include/linux/dma-direct.h:170 [inline] > dma_direct_map_sg+0x3bb/0x670 kernel/dma/direct.c:368 > dma_map_sg_attrs+0xd0/0x160 kernel/dma/mapping.c:183 > drm_gem_shmem_get_pages_sgt drivers/gpu/drm/drm_gem_shmem_helper.c:700 [inline] > drm_gem_shmem_get_pages_sgt+0x1fc/0x310 drivers/gpu/drm/drm_gem_shmem_helper.c:679 > virtio_gpu_object_shmem_init drivers/gpu/drm/virtio/virtgpu_object.c:153 [inline] > virtio_gpu_object_create+0x2fd/0xa70 drivers/gpu/drm/virtio/virtgpu_object.c:232 > virtio_gpu_gem_create drivers/gpu/drm/virtio/virtgpu_gem.c:45 [inline] > virtio_gpu_mode_dumb_create+0x298/0x530 drivers/gpu/drm/virtio/virtgpu_gem.c:85 > drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94 > drm_client_buffer_create drivers/gpu/drm/drm_client.c:267 [inline] > drm_client_framebuffer_create+0x1b7/0x770 drivers/gpu/drm/drm_client.c:412 > drm_fb_helper_generic_probe+0x1e5/0x810 drivers/gpu/drm/drm_fb_helper.c:2086 > drm_fb_helper_single_fb_probe drivers/gpu/drm/drm_fb_helper.c:1635 [inline] > __drm_fb_helper_initial_config_and_unlock+0xbc6/0x12d0 drivers/gpu/drm/drm_fb_helper.c:1793 > drm_fb_helper_initial_config drivers/gpu/drm/drm_fb_helper.c:1888 [inline] > drm_fb_helper_initial_config drivers/gpu/drm/drm_fb_helper.c:1880 [inline] > drm_fbdev_client_hotplug+0x2d4/0x580 drivers/gpu/drm/drm_fb_helper.c:2180 > drm_fbdev_generic_setup+0x1c8/0x450 drivers/gpu/drm/drm_fb_helper.c:2262 > virtio_gpu_probe+0x28f/0x2e0 drivers/gpu/drm/virtio/virtgpu_drv.c:127 > virtio_dev_probe+0x445/0x6f0 drivers/virtio/virtio.c:248 > really_probe+0x282/0x9f0 drivers/base/dd.c:553 > driver_probe_device+0xfe/0x1d0 drivers/base/dd.c:738 > device_driver_attach+0x228/0x290 drivers/base/dd.c:1013 > __driver_attach drivers/base/dd.c:1090 [inline] > __driver_attach+0xda/0x240 drivers/base/dd.c:1044 > bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:305 > bus_add_driver+0x348/0x5a0 drivers/base/bus.c:622 > driver_register+0x220/0x3a0 drivers/base/driver.c:171 > do_one_initcall+0x10a/0x7b0 init/main.c:1201 > do_initcall_level init/main.c:1274 [inline] > do_initcalls init/main.c:1290 [inline] > do_basic_setup init/main.c:1310 [inline] > kernel_init_freeable+0x589/0x638 init/main.c:1505 > kernel_init+0xd/0x1c0 init/main.c:1399 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > Modules linked in: > ---[ end trace 11a290451cfd19ed ]--- > RIP: 0010:swiotlb_map+0x5ac/0x700 kernel/dma/swiotlb.c:683 > Code: 28 04 00 00 48 c1 ea 03 80 3c 02 00 0f 85 4d 01 00 00 4c 8b a5 18 04 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 01 00 00 48 8d 7d 50 4d 8b 24 24 48 b8 00 00 > RSP: 0000:ffffc9000034f3e0 EFLAGS: 00010246 > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8162cc1d > RDX: 0000000000000000 RSI: ffffffff8162cc98 RDI: ffff88802971a470 > RBP: ffff88802971a048 R08: 0000000000000001 R09: ffffffff8c5dba77 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 000000007ac00000 R14: dffffc0000000000 R15: 0000000000001000 > FS: 0000000000000000(0000) GS:ffff88802ce00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00000000ffffffff CR3: 0000000009a8d000 CR4: 0000000000350ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400So it fails at 683 dev_WARN_ONCE(dev, 1, 684 "swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n", 685 &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit); which makes no sense to me as `dev` surely exists. I can see in the console log: virtio-pci 0000:00:01.0: vgaarb: deactivate vga console So what gives? Code: 28 04 00 00 48 c1 ea 03 80 3c 02 00 0f 85 4d 01 00 00 4c 8b a5 18 04 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 01 00 00 48 8d 7d 50 4d 8b 24 24 48 b8 00 00 is All code ======= 0: 28 04 00 sub %al,(%rax,%rax,1) 3: 00 48 c1 add %cl,-0x3f(%rax) 6: ea (bad) 7: 03 80 3c 02 00 0f add 0xf00023c(%rax),%eax d: 85 4d 01 test %ecx,0x1(%rbp) 10: 00 00 add %al,(%rax) 12: 4c 8b a5 18 04 00 00 mov 0x418(%rbp),%r12 19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 20: fc ff df 23: 4c 89 e2 mov %r12,%rdx 26: 48 c1 ea 03 shr $0x3,%rdx 2a:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction 2e: 0f 85 1e 01 00 00 jne 0x152 34: 48 8d 7d 50 lea 0x50(%rbp),%rdi 38: 4d 8b 24 24 mov (%r12),%r12 3c: 48 rex.W 3d: b8 .byte 0xb8 So %r12 was expected to have something valid, put in %rdx, and shifted by three (line 26). Then we fetch from base = 0000000000000000 (%rdx) + 0xdffffc0000000000(%rax)* scale 1. and compare against 0 (if I am reading this right). No clue here. I tried compiling the upstream kernel with the .config mentioned at the top but sadly I can't find anything that similar to this code to figure out what exactly it is trying to access and crash. CC-ing a fellow engineer who is debugging this, but it looks to be related to VirtIO DRM.> > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller at googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
Christoph Hellwig
2020-Aug-24 15:13 UTC
Is: virtio_gpu_object_shmem_init issues? Was:Re: upstream boot error: general protection fault in swiotlb_map
On Mon, Aug 24, 2020 at 11:06:51AM -0400, Konrad Rzeszutek Wilk wrote:> So it fails at > > 683 dev_WARN_ONCE(dev, 1, > 684 "swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n", > 685 &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit); > > > which makes no sense to me as `dev` surely exists. I can see in the console log: > > virtio-pci 0000:00:01.0: vgaarb: deactivate vga console > > So what gives?Well, look at the if around the WARN_ON - dma_capable failed on the swiotlb buffer. This means the virtio drm thingy has a dma mask (either the actual one set by the driver, or bus_dma_mask), which isn't enough to address the swiotlb buffer.
Dmitry Vyukov
2020-Aug-24 15:17 UTC
Is: virtio_gpu_object_shmem_init issues? Was:Re: upstream boot error: general protection fault in swiotlb_map
On Mon, Aug 24, 2020 at 5:07 PM Konrad Rzeszutek Wilk <konrad.wilk at oracle.com> wrote:> > On Thu, Aug 06, 2020 at 03:46:23AM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 47ec5303 Merge git://git.kernel.org/pub/scm/linux/kernel/g.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=16fe1dea900000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=7c06047f622c5724 > > dashboard link: https://syzkaller.appspot.com/bug?extid=3f86afd0b1e4bf1cb64c > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+3f86afd0b1e4bf1cb64c at syzkaller.appspotmail.com > > > > ceph: loaded (mds proto 32) > > NET: Registered protocol family 38 > > async_tx: api initialized (async) > > Key type asymmetric registered > > Asymmetric key parser 'x509' registered > > Asymmetric key parser 'pkcs8' registered > > Key type pkcs7_test registered > > Asymmetric key parser 'tpm_parser' registered > > Block layer SCSI generic (bsg) driver version 0.4 loaded (major 243) > > io scheduler mq-deadline registered > > io scheduler kyber registered > > io scheduler bfq registered > > hgafb: HGA card not detected. > > hgafb: probe of hgafb.0 failed with error -22 > > usbcore: registered new interface driver udlfb > > uvesafb: failed to execute /sbin/v86d > > uvesafb: make sure that the v86d helper is installed and executable > > uvesafb: Getting VBE info block failed (eax=0x4f00, err=-2) > > uvesafb: vbe_init() failed with -22 > > uvesafb: probe of uvesafb.0 failed with error -22 > > vga16fb: mapped to 0x000000008aac772d > > Console: switching to colour frame buffer device 80x30 > > fb0: VGA16 VGA frame buffer device > > input: Power Button as /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0 > > ACPI: Power Button [PWRF] > > ioatdma: Intel(R) QuickData Technology Driver 5.00 > > PCI Interrupt Link [GSIF] enabled at IRQ 21 > > PCI Interrupt Link [GSIG] enabled at IRQ 22 > > PCI Interrupt Link [GSIH] enabled at IRQ 23 > > N_HDLC line discipline registered with maxframe=4096 > > Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled > > 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A > > Cyclades driver 2.6 > > Initializing Nozomi driver 2.1d > > RocketPort device driver module, version 2.09, 12-June-2003 > > No rocketport ports found; unloading driver > > Non-volatile memory driver v1.3 > > Linux agpgart interface v0.103 > > [drm] Initialized vgem 1.0.0 20120112 for vgem on minor 0 > > [drm] Initialized vkms 1.0.0 20180514 for vkms on minor 1 > > usbcore: registered new interface driver udl > > [drm] pci: virtio-vga detected at 0000:00:01.0 > > fb0: switching to virtiodrmfb from VGA16 VGA > > Console: switching to colour VGA+ 80x25 > > virtio-pci 0000:00:01.0: vgaarb: deactivate vga console > > Console: switching to colour dummy device 80x25 > > [drm] features: -virgl +edid > > [drm] number of scanouts: 1 > > [drm] number of cap sets: 0 > > [drm] Initialized virtio_gpu 0.1.0 0 for virtio0 on minor 2 > > general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN > > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.8.0-syzkaller #0 > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 > > RIP: 0010:swiotlb_map+0x5ac/0x700 kernel/dma/swiotlb.c:683 > > Code: 28 04 00 00 48 c1 ea 03 80 3c 02 00 0f 85 4d 01 00 00 4c 8b a5 18 04 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 01 00 00 48 8d 7d 50 4d 8b 24 24 48 b8 00 00 > > RSP: 0000:ffffc9000034f3e0 EFLAGS: 00010246 > > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8162cc1d > > RDX: 0000000000000000 RSI: ffffffff8162cc98 RDI: ffff88802971a470 > > RBP: ffff88802971a048 R08: 0000000000000001 R09: ffffffff8c5dba77 > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > > R13: 000000007ac00000 R14: dffffc0000000000 R15: 0000000000001000 > > FS: 0000000000000000(0000) GS:ffff88802ce00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00000000ffffffff CR3: 0000000009a8d000 CR4: 0000000000350ef0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > dma_direct_map_page include/linux/dma-direct.h:170 [inline] > > dma_direct_map_sg+0x3bb/0x670 kernel/dma/direct.c:368 > > dma_map_sg_attrs+0xd0/0x160 kernel/dma/mapping.c:183 > > drm_gem_shmem_get_pages_sgt drivers/gpu/drm/drm_gem_shmem_helper.c:700 [inline] > > drm_gem_shmem_get_pages_sgt+0x1fc/0x310 drivers/gpu/drm/drm_gem_shmem_helper.c:679 > > virtio_gpu_object_shmem_init drivers/gpu/drm/virtio/virtgpu_object.c:153 [inline] > > virtio_gpu_object_create+0x2fd/0xa70 drivers/gpu/drm/virtio/virtgpu_object.c:232 > > virtio_gpu_gem_create drivers/gpu/drm/virtio/virtgpu_gem.c:45 [inline] > > virtio_gpu_mode_dumb_create+0x298/0x530 drivers/gpu/drm/virtio/virtgpu_gem.c:85 > > drm_mode_create_dumb+0x27c/0x300 drivers/gpu/drm/drm_dumb_buffers.c:94 > > drm_client_buffer_create drivers/gpu/drm/drm_client.c:267 [inline] > > drm_client_framebuffer_create+0x1b7/0x770 drivers/gpu/drm/drm_client.c:412 > > drm_fb_helper_generic_probe+0x1e5/0x810 drivers/gpu/drm/drm_fb_helper.c:2086 > > drm_fb_helper_single_fb_probe drivers/gpu/drm/drm_fb_helper.c:1635 [inline] > > __drm_fb_helper_initial_config_and_unlock+0xbc6/0x12d0 drivers/gpu/drm/drm_fb_helper.c:1793 > > drm_fb_helper_initial_config drivers/gpu/drm/drm_fb_helper.c:1888 [inline] > > drm_fb_helper_initial_config drivers/gpu/drm/drm_fb_helper.c:1880 [inline] > > drm_fbdev_client_hotplug+0x2d4/0x580 drivers/gpu/drm/drm_fb_helper.c:2180 > > drm_fbdev_generic_setup+0x1c8/0x450 drivers/gpu/drm/drm_fb_helper.c:2262 > > virtio_gpu_probe+0x28f/0x2e0 drivers/gpu/drm/virtio/virtgpu_drv.c:127 > > virtio_dev_probe+0x445/0x6f0 drivers/virtio/virtio.c:248 > > really_probe+0x282/0x9f0 drivers/base/dd.c:553 > > driver_probe_device+0xfe/0x1d0 drivers/base/dd.c:738 > > device_driver_attach+0x228/0x290 drivers/base/dd.c:1013 > > __driver_attach drivers/base/dd.c:1090 [inline] > > __driver_attach+0xda/0x240 drivers/base/dd.c:1044 > > bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:305 > > bus_add_driver+0x348/0x5a0 drivers/base/bus.c:622 > > driver_register+0x220/0x3a0 drivers/base/driver.c:171 > > do_one_initcall+0x10a/0x7b0 init/main.c:1201 > > do_initcall_level init/main.c:1274 [inline] > > do_initcalls init/main.c:1290 [inline] > > do_basic_setup init/main.c:1310 [inline] > > kernel_init_freeable+0x589/0x638 init/main.c:1505 > > kernel_init+0xd/0x1c0 init/main.c:1399 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > > Modules linked in: > > ---[ end trace 11a290451cfd19ed ]--- > > RIP: 0010:swiotlb_map+0x5ac/0x700 kernel/dma/swiotlb.c:683 > > Code: 28 04 00 00 48 c1 ea 03 80 3c 02 00 0f 85 4d 01 00 00 4c 8b a5 18 04 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 01 00 00 48 8d 7d 50 4d 8b 24 24 48 b8 00 00 > > RSP: 0000:ffffc9000034f3e0 EFLAGS: 00010246 > > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8162cc1d > > RDX: 0000000000000000 RSI: ffffffff8162cc98 RDI: ffff88802971a470 > > RBP: ffff88802971a048 R08: 0000000000000001 R09: ffffffff8c5dba77 > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > > R13: 000000007ac00000 R14: dffffc0000000000 R15: 0000000000001000 > > FS: 0000000000000000(0000) GS:ffff88802ce00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00000000ffffffff CR3: 0000000009a8d000 CR4: 0000000000350ef0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > So it fails at > > 683 dev_WARN_ONCE(dev, 1, > 684 "swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n", > 685 &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit); > > > which makes no sense to me as `dev` surely exists. I can see in the console log: > > virtio-pci 0000:00:01.0: vgaarb: deactivate vga console > > So what gives? > > Code: 28 04 00 00 48 c1 ea 03 80 3c 02 00 0f 85 4d 01 00 00 4c 8b a5 18 04 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 1e 01 00 00 48 8d 7d 50 4d 8b 24 24 48 b8 00 00 > is > All code > =======> 0: 28 04 00 sub %al,(%rax,%rax,1) > 3: 00 48 c1 add %cl,-0x3f(%rax) > 6: ea (bad) > 7: 03 80 3c 02 00 0f add 0xf00023c(%rax),%eax > d: 85 4d 01 test %ecx,0x1(%rbp) > 10: 00 00 add %al,(%rax) > 12: 4c 8b a5 18 04 00 00 mov 0x418(%rbp),%r12 > 19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax > 20: fc ff df > 23: 4c 89 e2 mov %r12,%rdx > 26: 48 c1 ea 03 shr $0x3,%rdx > 2a:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction > 2e: 0f 85 1e 01 00 00 jne 0x152 > 34: 48 8d 7d 50 lea 0x50(%rbp),%rdi > 38: 4d 8b 24 24 mov (%r12),%r12 > 3c: 48 rex.W > 3d: b8 .byte 0xb8 > > So %r12 was expected to have something valid, put in %rdx, and shifted by three (line 26). Then > we fetch from > base = 0000000000000000 (%rdx) + 0xdffffc0000000000(%rax)* scale 1. > > and compare against 0 (if I am reading this right). > > No clue here.Hi Konrad, This 0xdffffc0000000000 access is KASAN instrumentation to check shadow memory. Since KASAN did not produce any bug report, most likely it is irrelevant here.> I tried compiling the upstream kernel with the .config mentioned at the top > but sadly I can't find anything that similar to this code to figure out > what exactly it is trying to access and crash. > > CC-ing a fellow engineer who is debugging this, but it looks to be related to VirtIO DRM. > > > > > > > --- > > This report is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller at googlegroups.com. > > > > syzbot will keep track of this issue. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe at googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20200824150650.GD21321%40char.us.oracle.com.
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