[ 3.8.y.z extended stable ] Patch "SUNRPC: Fix memory corruption issue on 32-bit highmem systems" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Thu Sep 5 20:49:44 UTC 2013


This is a note to let you know that I have just added a patch titled

    SUNRPC: Fix memory corruption issue on 32-bit highmem systems

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 55fd127db4884c86ab4b299c688962c798a0646c Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust at netapp.com>
Date: Wed, 28 Aug 2013 13:35:13 -0400
Subject: SUNRPC: Fix memory corruption issue on 32-bit highmem systems

commit 347e2233b7667e336d9f671f1a52dfa3f0416e2c upstream.

Some architectures, such as ARM-32 do not return the same base address
when you call kmap_atomic() twice on the same page.
This causes problems for the memmove() call in the XDR helper routine
"_shift_data_right_pages()", since it defeats the detection of
overlapping memory ranges, and has been seen to corrupt memory.

The fix is to distinguish between the case where we're doing an
inter-page copy or not. In the former case of we know that the memory
ranges cannot possibly overlap, so we can additionally micro-optimise
by replacing memmove() with memcpy().

Reported-by: Mark Young <MYoung at nvidia.com>
Reported-by: Matt Craighead <mcraighead at nvidia.com>
Cc: Bruce Fields <bfields at fieldses.org>
Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Tested-by: Matt Craighead <mcraighead at nvidia.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sunrpc/xdr.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 5605563..ddbec19 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -207,10 +207,13 @@ _shift_data_right_pages(struct page **pages, size_t pgto_base,
 		pgfrom_base -= copy;

 		vto = kmap_atomic(*pgto);
-		vfrom = kmap_atomic(*pgfrom);
-		memmove(vto + pgto_base, vfrom + pgfrom_base, copy);
+		if (*pgto != *pgfrom) {
+			vfrom = kmap_atomic(*pgfrom);
+			memcpy(vto + pgto_base, vfrom + pgfrom_base, copy);
+			kunmap_atomic(vfrom);
+		} else
+			memmove(vto + pgto_base, vto + pgfrom_base, copy);
 		flush_dcache_page(*pgto);
-		kunmap_atomic(vfrom);
 		kunmap_atomic(vto);

 	} while ((len -= copy) != 0);
--
1.8.1.2





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