[ 66/89] md: Avoid write invalid address if read_seqretry returned true.

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: majianpeng <majianpeng@xxxxxxxxx>

commit 35f9ac2dcec8f79d7059ce174fd7b7ee3290d620 upstream.

If read_seqretry returned true and bbp was changed, it will write
invalid address which can cause some serious problem.

This bug was introduced by commit v3.0-rc7-130-g2699b67.
So fix is suitable for 3.0.y thru 3.6.y.

Reported-by: zhuwenfeng@xxxxxxxxxxx
Tested-by: zhuwenfeng@xxxxxxxxxxx
Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/md/md.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 14db6ab..4c7d880 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1817,10 +1817,10 @@ retry:
 			memset(bbp, 0xff, PAGE_SIZE);
 
 			for (i = 0 ; i < bb->count ; i++) {
-				u64 internal_bb = *p++;
+				u64 internal_bb = p[i];
 				u64 store_bb = ((BB_OFFSET(internal_bb) << 10)
 						| BB_LEN(internal_bb));
-				*bbp++ = cpu_to_le64(store_bb);
+				bbp[i] = cpu_to_le64(store_bb);
 			}
 			bb->changed = 0;
 			if (read_seqretry(&bb->lock, seq))


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