Messages in this thread | | | Subject | Re: [PATCH] dma-direct: Fix potential NULL pointer dereference | From | Thomas Tai <> | Date | Tue, 15 Sep 2020 10:11:51 -0400 |
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On 2020-09-15 10:07 a.m., Christoph Hellwig wrote: > On Tue, Sep 15, 2020 at 08:03:14AM -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(). It is because dev->dma_mask >> can potentially be a null pointer. Using the dma_get_mask() macro can >> avoid the NULL pointer dereference. > > dma_mask must not be zero. This means drm is calling DMA API functions > on something weird. This needs to be fixed in the caller. >
Thanks, Christoph for your comment. The caller already fixed the null pointer in the latest v5.9-rc5. I am thinking that if we had used the dma_get_mask(), the kernel couldn't panic and could properly print out the warning message.
Thomas
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