md: Avoid write invalid address if read_seqretry returned true.

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@kedacom.com
Tested-by: zhuwenfeng@kedacom.com
Cc: stable@vger.kernel.org
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 14db6abb2c42..4c7d880a60a4 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))