Patch "ext4: validate that metadata blocks do not overlap superblock" has been added to the 4.7-stable tree

[<gregkh@linuxfoundation.org>]

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

    ext4: validate that metadata blocks do not overlap superblock

to the 4.7-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-validate-that-metadata-blocks-do-not-overlap-superblock.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 829fa70dddadf9dd041d62b82cd7cea63943899d Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Mon, 1 Aug 2016 00:51:02 -0400
Subject: ext4: validate that metadata blocks do not overlap superblock

From: Theodore Ts'o <tytso@mit.edu>

commit 829fa70dddadf9dd041d62b82cd7cea63943899d upstream.

A number of fuzzing failures seem to be caused by allocation bitmaps
or other metadata blocks being pointed at the superblock.

This can cause kernel BUG or WARNings once the superblock is
overwritten, so validate the group descriptor blocks to make sure this
doesn't happen.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/super.c |   18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2131,6 +2131,7 @@ void ext4_group_desc_csum_set(struct sup
 
 /* Called at mount-time, super-block is locked */
 static int ext4_check_descriptors(struct super_block *sb,
+				  ext4_fsblk_t sb_block,
 				  ext4_group_t *first_not_zeroed)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
@@ -2161,6 +2162,11 @@ static int ext4_check_descriptors(struct
 			grp = i;
 
 		block_bitmap = ext4_block_bitmap(sb, gdp);
+		if (block_bitmap == sb_block) {
+			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
+				 "Block bitmap for group %u overlaps "
+				 "superblock", i);
+		}
 		if (block_bitmap < first_block || block_bitmap > last_block) {
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
 			       "Block bitmap for group %u not in group "
@@ -2168,6 +2174,11 @@ static int ext4_check_descriptors(struct
 			return 0;
 		}
 		inode_bitmap = ext4_inode_bitmap(sb, gdp);
+		if (inode_bitmap == sb_block) {
+			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
+				 "Inode bitmap for group %u overlaps "
+				 "superblock", i);
+		}
 		if (inode_bitmap < first_block || inode_bitmap > last_block) {
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
 			       "Inode bitmap for group %u not in group "
@@ -2175,6 +2186,11 @@ static int ext4_check_descriptors(struct
 			return 0;
 		}
 		inode_table = ext4_inode_table(sb, gdp);
+		if (inode_table == sb_block) {
+			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
+				 "Inode table for group %u overlaps "
+				 "superblock", i);
+		}
 		if (inode_table < first_block ||
 		    inode_table + sbi->s_itb_per_group - 1 > last_block) {
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@@ -3677,7 +3693,7 @@ static int ext4_fill_super(struct super_
 			goto failed_mount2;
 		}
 	}
-	if (!ext4_check_descriptors(sb, &first_not_zeroed)) {
+	if (!ext4_check_descriptors(sb, logical_sb_block, &first_not_zeroed)) {
 		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
 		ret = -EFSCORRUPTED;
 		goto failed_mount2;


Patches currently in stable-queue which might be from tytso@mit.edu are

queue-4.7/ext4-fix-xattr-shifting-when-expanding-inodes-part-2.patch
queue-4.7/ext4-fix-xattr-shifting-when-expanding-inodes.patch
queue-4.7/ext4-avoid-deadlock-when-expanding-inode-size.patch
queue-4.7/ext4-avoid-modifying-checksum-fields-directly-during-checksum-verification.patch
queue-4.7/ext4-validate-that-metadata-blocks-do-not-overlap-superblock.patch