2 files changed, 15 insertions, 2 deletions

diff --git a/fs/sysv/super.c b/fs/sysv/super.c
index 2da3075aff78..3785262b98e0 100644
--- a/fs/sysv/super.c
+++ b/fs/sysv/super.c
@@ -469,7 +469,7 @@ static int v7_fill_super(struct super_block *sb, void *data, int silent)
         v7sb = (struct v7_super_block *) bh->b_data;
         if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
             fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
-            fs32_to_cpu(sbi, v7sb->s_time) == 0)
+            fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
                 goto failed;
 
         /* plausibility check on root inode: it is a directory,
@@ -479,7 +479,9 @@ static int v7_fill_super(struct super_block *sb, void *data, int silent)
         v7i = (struct sysv_inode *)(bh2->b_data + 64);
         if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
             (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
-            (fs32_to_cpu(sbi, v7i->i_size) & 017) != 0)
+            (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
+            (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
+             sizeof(struct sysv_dir_entry)))
                 goto failed;
         brelse(bh2);
         bh2 = NULL;
diff --git a/include/linux/sysv_fs.h b/include/linux/sysv_fs.h
index 96411306eec6..e47d6d90023d 100644
--- a/include/linux/sysv_fs.h
+++ b/include/linux/sysv_fs.h
@@ -148,6 +148,17 @@ struct v7_super_block {
         char    s_fname[6];     /* file system name */
         char    s_fpack[6];     /* file system pack name */
 };
+/* Constants to aid sanity checking */
+/* This is not a hard limit, nor enforced by v7 kernel. It's actually just
+ * the limit used by Seventh Edition's ls, though is high enough to assume
+ * that no reasonable file system would have that much entries in root
+ * directory. Thus, if we see anything higher, we just probably got the
+ * endiannes wrong. */
+#define V7_NFILES       1024
+/* The disk addresses are three-byte (despite direct block addresses being
+ * aligned word-wise in inode). If the most significant byte is non-zero,
+ * something is most likely wrong (not a filesystem, bad bytesex). */
+#define V7_MAXSIZE      0x00ffffff
 
 /* Coherent super-block data on disk */
 #define COH_NICINOD     100     /* number of inode cache entries */