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

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: Willy Tarreau <w@1wt.eu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 046e3e93783ec1b1880a6233b297215f07f5eb92..f9c938e21e659af5b8e04cee21065dbf8fec3cbe 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -246,6 +246,7 @@ 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 6cf69fa212fb18e1bec8da7ff7dd6c124653b79a..faa192087033c340ffb89c7c029b44e80eb8aa3e 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3537,7 +3537,15 @@ 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;
        }
 
@@ -3652,6 +3660,13 @@ 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 =