[PATCH V2] dma-direct: Fix potential NULL pointer dereference

[PATCH V2] dma-direct: Fix potential NULL pointer dereference

[Thomas Tai]

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.tai@oracle.com>
---
 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

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Re: [PATCH V2] dma-direct: Fix potential NULL pointer dereference

[Konrad Rzeszutek Wilk]

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.tai@oracle.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

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
> 
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Re: [PATCH V2] dma-direct: Fix potential NULL pointer dereference

[Christoph Hellwig]

Thanks,

applied to the dma-mapping for-next tree.
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Re: [PATCH V2] dma-direct: Fix potential NULL pointer dereference

[Thomas Tai]

On 2020-09-17 12:44 p.m., Christoph Hellwig wrote:
> Thanks,
> 
> applied to the dma-mapping for-next tree.

Thank you, Christoph for suggesting and applying the fix.

Thomas

> 
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Re: [PATCH V2] dma-direct: Fix potential NULL pointer dereference

[Thomas Tai]

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.tai@oracle.com>
> 
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@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
>>
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