ext4: sanity check the block and cluster size at mount time

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>
Cc: stable@vger.kernel.org

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 53d6d463ac4d62436973b6c7a2fcfb9302c628f3..bdf1e5ee8642aa929294e8f397d38811ae1f7566 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -235,6 +235,7 @@ 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_CLUSTER_LOG_SIZE      30
 #ifdef __KERNEL__
 # define EXT4_BLOCK_SIZE(s)            ((s)->s_blocksize)
 #else

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 35ccbdc2d64e4072071409813a959ed3b922e5f5..0f9ae4ce33d610aeb0269ae843c8c18410c798b7 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3567,7 +3567,15 @@ 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,
-                      "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;
        }
 
@@ -3699,6 +3707,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                                 "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 =