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List:       linux-stable-commits
Subject:    Patch "net/rds: dma_map_sg is entitled to merge entries" has been added to the 5.4-stable tree
From:       Sasha Levin <sashal () kernel ! org>
Date:       2021-08-30 19:22:50
Message-ID: 20210830192251.76CF3600AA () mail ! kernel ! org
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This is a note to let you know that I've just added the patch titled

    net/rds: dma_map_sg is entitled to merge entries

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-rds-dma_map_sg-is-entitled-to-merge-entries.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.



commit 475b5d355df94352f5afa76ada1d27b192c992ce
Author: Gerd Rausch <gerd.rausch@oracle.com>
Date:   Tue Aug 17 10:04:37 2021 -0700

    net/rds: dma_map_sg is entitled to merge entries
    
    [ Upstream commit fb4b1373dcab086d0619c29310f0466a0b2ceb8a ]
    
    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 c588072bba6b ("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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
index 06ecf9d2d4bf..ef6acd721118 100644
--- a/net/rds/ib_frmr.c
+++ b/net/rds/ib_frmr.c
@@ -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,
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