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net/rds: dma_map_sg is entitled to merge entries

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Function "dma_map_sg" is entitled to merge adjacent entries
and return a value smaller than what was passed as "nents".

Subsequently "ib_map_mr_sg" needs to work with this value ("sg_dma_len")
rather than the original "nents" parameter ("sg_len").

This old RDS bug was exposed and reliably causes kernel panics
(using RDMA operations "rds-stress -D") on x86_64 starting with:
commit c588072bba ("iommu/vt-d: Convert intel iommu driver to the iommu ops")

Simply put: Linux 5.11 and later.

Signed-off-by: Gerd Rausch <gerd.rausch@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Link: https://lore.kernel.org/r/60efc69f-1f35-529d-a7ef-da0549cad143@oracle.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Gerd Rausch 2021-08-17 10:04:37 -07:00 committed by Jakub Kicinski
parent c1930148a3
commit fb4b1373dc
1 changed files with 2 additions and 2 deletions
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4
net/rds/ib_frmr.c
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@ -131,9 +131,9 @@ static int rds_ib_post_reg_frmr(struct rds_ib_mr *ibmr)
cpu_relax();
}
ret = ib_map_mr_sg_zbva(frmr->mr, ibmr->sg, ibmr->sg_len,
ret = ib_map_mr_sg_zbva(frmr->mr, ibmr->sg, ibmr->sg_dma_len,
&off, PAGE_SIZE);
if (unlikely(ret != ibmr->sg_len))
if (unlikely(ret != ibmr->sg_dma_len))
return ret < 0 ? ret : -EINVAL;
if (cmpxchg(&frmr->fr_state,