On 2020-09-17 12:05 p.m., Konrad Rzeszutek Wilk wrote:
On Wed, Sep 16, 2020 at 02:51:06PM -0600, Thomas Tai wrote:When booting the kernel v5.9-rc4 on a VM, the kernel would panic when printing a warning message in swiotlb_map(). The dev->dma_mask must not be a NULL pointer when calling the dma mapping layer. A NULL pointer check can potentially avoid the panic. [drm] Initialized virtio_gpu 0.1.0 0 for virtio0 on minor 0 BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 1 PID: 331 Comm: systemd-udevd Not tainted 5.9.0-rc4 #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1 04/01/2014 RIP: 0010:swiotlb_map+0x1ac/0x200 Code: e8 d9 fc ff ff 80 3d 92 ee 4c 01 00 75 51 49 8b 84 24 48 02 00 00 4d 8b 6c 24 50 c6 05 7c ee 4c 01 01 4d 8b bc 24 58 02 00 00 <4c> 8b 30 4d 85 ed 75 04 4d 8b 2c 24 4c 89 e7 e8 10 6b 4f 00 4d 89 RSP: 0018:ffff9f96801af6f8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000001000 RCX: 0000000000000080 RDX: 000000000000007f RSI: 0000000000000202 RDI: 0000000000000202 RBP: ffff9f96801af748 R08: ffffffffffffffff R09: 0000000000000020 R10: 0000000000000000 R11: ffff8fabfffa3000 R12: ffff8faad02c7810 R13: 0000000000000000 R14: 0000000000000020 R15: 0000000000000000 FS: 00007fabc63588c0(0000) GS:ffff8fabf7c80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000151496005 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: dma_direct_map_sg+0x124/0x210 dma_map_sg_attrs+0x32/0x50 drm_gem_shmem_get_pages_sgt+0x6a/0x90 [drm] virtio_gpu_object_create+0x140/0x2f0 [virtio_gpu] ? ww_mutex_unlock+0x26/0x30 virtio_gpu_mode_dumb_create+0xab/0x160 [virtio_gpu] drm_mode_create_dumb+0x82/0x90 [drm] drm_client_framebuffer_create+0xaa/0x200 [drm] drm_fb_helper_generic_probe+0x59/0x150 [drm_kms_helper] drm_fb_helper_single_fb_probe+0x29e/0x3e0 [drm_kms_helper] __drm_fb_helper_initial_config_and_unlock+0x41/0xd0 [drm_kms_helper] drm_fbdev_client_hotplug+0xe6/0x1a0 [drm_kms_helper] drm_fbdev_generic_setup+0xaf/0x170 [drm_kms_helper] virtio_gpu_probe+0xea/0x100 [virtio_gpu] virtio_dev_probe+0x14b/0x1e0 [virtio] really_probe+0x1db/0x440 driver_probe_device+0xe9/0x160 device_driver_attach+0x5d/0x70 __driver_attach+0x8f/0x150 ? device_driver_attach+0x70/0x70 bus_for_each_dev+0x7e/0xc0 driver_attach+0x1e/0x20 bus_add_driver+0x152/0x1f0 driver_register+0x74/0xd0 ? 0xffffffffc0529000 register_virtio_driver+0x20/0x30 [virtio] virtio_gpu_driver_init+0x15/0x1000 [virtio_gpu] do_one_initcall+0x4a/0x1fa ? _cond_resched+0x19/0x30 ? kmem_cache_alloc_trace+0x16b/0x2e0 do_init_module+0x62/0x240 load_module+0xe0e/0x1100 ? security_kernel_post_read_file+0x5c/0x70 __do_sys_finit_module+0xbe/0x120 ? __do_sys_finit_module+0xbe/0x120 __x64_sys_finit_module+0x1a/0x20 do_syscall_64+0x38/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Thomas Tai <thomas....@oracle.com>Reviewed-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Thank you, Konrad for reviewing the fix. Thomas
Thank you!--- include/linux/dma-direct.h | 3 --- kernel/dma/mapping.c | 11 +++++++++++ 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h index 6e87225..0648708 100644 --- a/include/linux/dma-direct.h +++ b/include/linux/dma-direct.h @@ -62,9 +62,6 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, { dma_addr_t end = addr + size - 1;- if (!dev->dma_mask)- return false; - if (is_ram && !IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) && min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn))) return false; diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 0d12942..7133d5c 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -144,6 +144,10 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page, dma_addr_t addr;BUG_ON(!valid_dma_direction(dir));+ + if (WARN_ON_ONCE(!dev->dma_mask)) + return DMA_MAPPING_ERROR; + if (dma_map_direct(dev, ops)) addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); else @@ -179,6 +183,10 @@ int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, int ents;BUG_ON(!valid_dma_direction(dir));+ + if (WARN_ON_ONCE(!dev->dma_mask)) + return 0; + if (dma_map_direct(dev, ops)) ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); else @@ -213,6 +221,9 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,BUG_ON(!valid_dma_direction(dir)); + if (WARN_ON_ONCE(!dev->dma_mask))+ return DMA_MAPPING_ERROR; + /* Don't allow RAM to be mapped */ if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr)))) return DMA_MAPPING_ERROR; -- 1.8.3.1
