xprtrdma: Fix DMA scatter-gather list mapping imbalance
authorChuck Lever <chuck.lever@oracle.com>
Wed, 12 Feb 2020 16:12:30 +0000 (11:12 -0500)
committerAnna Schumaker <Anna.Schumaker@Netapp.com>
Thu, 13 Feb 2020 20:35:33 +0000 (15:35 -0500)
commitca1c671302825182629d3c1a60363cee6f5455bb
tree3d73e0b5bab64840f7c824f8469ec9464a99e12a
parentefeda80da38d0b4afd77a12bd4a44f657567d26c
xprtrdma: Fix DMA scatter-gather list mapping imbalance

The @nents value that was passed to ib_dma_map_sg() has to be passed
to the matching ib_dma_unmap_sg() call. If ib_dma_map_sg() choses to
concatenate sg entries, it will return a different nents value than
it was passed.

The bug was exposed by recent changes to the AMD IOMMU driver, which
enabled sg entry concatenation.

Looking all the way back to commit 4143f34e01e9 ("xprtrdma: Port to
new memory registration API") and reviewing other kernel ULPs, it's
not clear that the frwr_map() logic was ever correct for this case.

Reported-by: Andre Tomt <andre@tomt.net>
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
net/sunrpc/xprtrdma/frwr_ops.c