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Patch "ext4: validate that metadata blocks do not overlap superblock" has been added to the 3.14-stable tree

PATCH [email protected] 1 participant 1 message Sep 9, 2016

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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 3.14-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-3.14 subdirectory.

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

Quoted 1 line

From 829fa70dddadf9dd041d62b82cd7cea63943899d Mon Sep 17 00:00:00 2001

From: Theodore Ts'o <[email protected]>
Date: Mon, 1 Aug 2016 00:51:02 -0400
Subject: ext4: validate that metadata blocks do not overlap superblock

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

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.

---
 fs/ext4/super.c |   18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)
fs/ext4/super.c +17 -1
@@ -2071,6 +2071,7 @@ 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);
@@ -2101,6 +2102,11 @@ 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 "
@@ -2108,6 +2114,11 @@ 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 "
@@ -2115,6 +2126,11 @@ 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: "
@@ -3869,7 +3885,7 @@ 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!");
 		goto failed_mount2;
 	}

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

queue-3.14/ext4-validate-that-metadata-blocks-do-not-overlap-superblock.patch