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>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 14db6abb2c4209fb5b81def823b6b7b8473fa38d..4c7d880a60a4ed41210c813ddb2af1a9f22005e9 100644 (file)
--- 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))