[PATCH 3/4] ext4: don't allow r/w mounts if metadata blocks overlap the superblock

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From: Theodore Ts'o <tytso@xxxxxxx>

If some metadata block, such as an allocation bitmap, overlaps the
superblock, it's very likely that if the file system is mounted
read/write, the results will not be pretty.  So disallow r/w mounts
for file systems corrupted in this particular way.

Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Harsh Shandilya <harsh@xxxxxxxx>
---
 fs/ext4/super.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index cc0a2298099d..263a2f9802f8 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2093,6 +2093,8 @@ static int ext4_check_descriptors(struct super_block *sb,
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
 				 "Block bitmap for group %u overlaps "
 				 "superblock", i);
+			if (!sb_rdonly(sb))
+				return 0;
 		}
 		if (block_bitmap < first_block || block_bitmap > last_block) {
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@@ -2105,6 +2107,8 @@ static int ext4_check_descriptors(struct super_block *sb,
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
 				 "Inode bitmap for group %u overlaps "
 				 "superblock", i);
+			if (!sb_rdonly(sb))
+				return 0;
 		}
 		if (inode_bitmap < first_block || inode_bitmap > last_block) {
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
@@ -2117,6 +2121,8 @@ static int ext4_check_descriptors(struct super_block *sb,
 			ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
 				 "Inode table for group %u overlaps "
 				 "superblock", i);
+			if (!sb_rdonly(sb))
+				return 0;
 		}
 		if (inode_table < first_block ||
 		    inode_table + sbi->s_itb_per_group - 1 > last_block) {
-- 
2.15.0.2308.g658a28aa74af




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