ext4: sanity check the block and cluster size at mount time
authorTheodore Ts'o <tytso@mit.edu>
Fri, 18 Nov 2016 18:00:24 +0000 (13:00 -0500)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 23 Feb 2017 03:51:01 +0000 (03:51 +0000)
commit 8cdf3372fe8368f56315e66bea9f35053c418093 upstream.

If the block size or cluster size is insane, reject the mount.  This
is important for security reasons (although we shouldn't be just
depending on this check).

Ref: http://www.securityfocus.com/archive/1/539661
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1332506
Reported-by: Borislav Petkov <bp@alien8.de>
Reported-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
fs/ext4/ext4.h
fs/ext4/super.c

index 8c8115c..eef0d1a 100644 (file)
@@ -244,6 +244,7 @@ struct ext4_io_submit {
 #define        EXT4_MAX_BLOCK_SIZE             65536
 #define EXT4_MIN_BLOCK_LOG_SIZE                10
 #define EXT4_MAX_BLOCK_LOG_SIZE                16
 #define        EXT4_MAX_BLOCK_SIZE             65536
 #define EXT4_MIN_BLOCK_LOG_SIZE                10
 #define EXT4_MAX_BLOCK_LOG_SIZE                16
+#define EXT4_MAX_CLUSTER_LOG_SIZE      30
 #ifdef __KERNEL__
 # define EXT4_BLOCK_SIZE(s)            ((s)->s_blocksize)
 #else
 #ifdef __KERNEL__
 # define EXT4_BLOCK_SIZE(s)            ((s)->s_blocksize)
 #else
index 7266a2e..e3ccddb 100644 (file)
@@ -3451,7 +3451,15 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
        if (blocksize < EXT4_MIN_BLOCK_SIZE ||
            blocksize > EXT4_MAX_BLOCK_SIZE) {
                ext4_msg(sb, KERN_ERR,
        if (blocksize < EXT4_MIN_BLOCK_SIZE ||
            blocksize > EXT4_MAX_BLOCK_SIZE) {
                ext4_msg(sb, KERN_ERR,
-                      "Unsupported filesystem blocksize %d", blocksize);
+                      "Unsupported filesystem blocksize %d (%d log_block_size)",
+                        blocksize, le32_to_cpu(es->s_log_block_size));
+               goto failed_mount;
+       }
+       if (le32_to_cpu(es->s_log_block_size) >
+           (EXT4_MAX_BLOCK_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
+               ext4_msg(sb, KERN_ERR,
+                        "Invalid log block size: %u",
+                        le32_to_cpu(es->s_log_block_size));
                goto failed_mount;
        }
 
                goto failed_mount;
        }
 
@@ -3568,6 +3576,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                                 "block size (%d)", clustersize, blocksize);
                        goto failed_mount;
                }
                                 "block size (%d)", clustersize, blocksize);
                        goto failed_mount;
                }
+               if (le32_to_cpu(es->s_log_cluster_size) >
+                   (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
+                       ext4_msg(sb, KERN_ERR,
+                                "Invalid log cluster size: %u",
+                                le32_to_cpu(es->s_log_cluster_size));
+                       goto failed_mount;
+               }
                sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
                        le32_to_cpu(es->s_log_block_size);
                sbi->s_clusters_per_group =
                sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
                        le32_to_cpu(es->s_log_block_size);
                sbi->s_clusters_per_group =