Patch "ext4: add sanity checking to count_overhead()" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

ext4: add sanity checking to count_overhead()

to the 4.8-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:
ext4-add-sanity-checking-to-count_overhead.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Theodore Ts'o <[email protected]>
Date: Fri, 18 Nov 2016 13:37:47 -0500
Subject: ext4: add sanity checking to count_overhead()

From: Theodore Ts'o <[email protected]>

commit c48ae41bafe31e9a66d8be2ced4e42a6b57fa814 upstream.

The commit "ext4: sanity check the block and cluster size at mount time" should prevent any problems, but in case the superblock is modified while the file system is mounted, add an extra safety check to make sure we won't overrun the allocated buffer.

---
 fs/ext4/super.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

@@ -3161,10 +3161,15 @@ static int count_overhead(struct super_b
 			ext4_set_bit(s++, buf);
 			count++;
 		}
-		for (j = ext4_bg_num_gdb(sb, grp); j > 0; j--) {
-			ext4_set_bit(EXT4_B2C(sbi, s++), buf);
-			count++;
+		j = ext4_bg_num_gdb(sb, grp);
+		if (s + j > EXT4_BLOCKS_PER_GROUP(sb)) {
+			ext4_error(sb, "Invalid number of block group "
+				   "descriptor blocks: %d", j);
+			j = EXT4_BLOCKS_PER_GROUP(sb) - s;
 		}
+		count += j;
+		for (; j > 0; j--)
+			ext4_set_bit(EXT4_B2C(sbi, s++), buf);
 	}
 	if (!count)
 		return 0;

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/ext4-reject-inodes-with-negative-size.patch queue-4.8/ext4-fix-in-superblock-mount-options-processing.patch queue-4.8/ext4-fix-mballoc-breakage-with-64k-block-size.patch queue-4.8/ext4-do-not-perform-data-journaling-when-data-is-encrypted.patch queue-4.8/ext4-use-more-strict-checks-for-inodes_per_block-on-mount.patch queue-4.8/ext4-add-sanity-checking-to-count_overhead.patch queue-4.8/ext4-return-enomem-instead-of-success.patch queue-4.8/ext4-fix-stack-memory-corruption-with-64k-block-size.patch