ext4: verify the depth of extent tree in ext4_find_extent()
authorTheodore Ts'o <tytso@mit.edu>
Thu, 14 Jun 2018 16:55:10 +0000 (12:55 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 11 Jul 2018 14:29:17 +0000 (16:29 +0200)
commit bc890a60247171294acc0bd67d211fa4b88d40ba upstream.

If there is a corupted file system where the claimed depth of the
extent tree is -1, this can cause a massive buffer overrun leading to
sadness.

This addresses CVE-2018-10877.

https://bugzilla.kernel.org/show_bug.cgi?id=199417

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ext4/ext4_extents.h
fs/ext4/extents.c

index 8ecf84b..a284fb2 100644 (file)
@@ -103,6 +103,7 @@ struct ext4_extent_header {
 };
 
 #define EXT4_EXT_MAGIC         cpu_to_le16(0xf30a)
+#define EXT4_MAX_EXTENT_DEPTH 5
 
 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \
        (sizeof(struct ext4_extent_header) + \
index 883e89a..5592b77 100644 (file)
@@ -881,6 +881,12 @@ ext4_find_extent(struct inode *inode, ext4_lblk_t block,
 
        eh = ext_inode_hdr(inode);
        depth = ext_depth(inode);
+       if (depth < 0 || depth > EXT4_MAX_EXTENT_DEPTH) {
+               EXT4_ERROR_INODE(inode, "inode has invalid extent depth: %d",
+                                depth);
+               ret = -EFSCORRUPTED;
+               goto err;
+       }
 
        if (path) {
                ext4_ext_drop_refs(path);