Messages in this thread | | | Date | Tue, 17 May 2022 11:18:54 +0100 | Subject | Re: [PATCH] iommu/dma: Fix check for error return from iommu_map_sg_atomic() | From | Robin Murphy <> |
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On 2022-05-17 11:17, Niklas Schnelle wrote: > On Tue, 2022-05-17 at 10:36 +0200, Christoph Hellwig wrote: >> On Fri, May 13, 2022 at 05:39:48PM +0200, Niklas Schnelle wrote: >>> In __iommu_dma_alloc_noncontiguous() the value returned by >>> iommu_map_sg_atomic() is checked for being smaller than size. Before >>> commit ad8f36e4b6b1 ("iommu: return full error code from >>> iommu_map_sg[_atomic]()") this simply checked if the requested size was >>> successfully mapped. >>> >>> After that commit iommu_map_sg_atomic() may also return a negative >>> error value. In principle this too would be covered by the existing >>> check. There is one problem however, as size is of type size_t while the >>> return type of iommu_map_sg_atomic() is now of type ssize_t the latter gets >>> converted to size_t and negative error values end up as very large >>> positive values making the check succeed. Fix this by making the return >>> type visible with a local variable and add an explicit cast to ssize_t. >>> >>> Fixes: ad8f36e4b6b1 ("iommu: return full error code from iommu_map_sg[_atomic]()") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> >> >> I don't see what the point of the newly added local variable is here. >> Just casting size should be all that is needed as far as I can tell. > > No technical reason just found it easier to read and more descriptive. > I'll sent a v2 with just the cast, it does simplify the commit message.
Note that this is already fixed upstream, though:
https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git/commit/?h=core&id=a3884774d731f03d3a3dd4fb70ec2d9341ceb39d
Robin.
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