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authorPhillip Lougher <phillip@lougher.demon.co.uk>2011-05-24 04:33:34 +0100
committerPhillip Lougher <phillip@lougher.demon.co.uk>2011-05-25 18:21:33 +0100
commit1cac63cc9b2ff0d16ab2d16232b1a6ee8676a47b (patch)
tree31ee36dac4a1b351c153058ffa0799a959ba0272
parentac51a0a7139aa93bf1176b701c86fa3d2bdf6106 (diff)
Squashfs: add sanity checks to fragment reading at mount time
Fsfuzzer generates corrupted filesystems which throw a warn_on in kmalloc. One of these is due to a corrupted superblock fragments field. Fix this by checking that the number of bytes to be read (and allocated) does not extend into the next filesystem structure. Also add a couple of other sanity checks of the mount-time fragment table structures. Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
-rw-r--r--fs/squashfs/fragment.c24
-rw-r--r--fs/squashfs/squashfs.h2
-rw-r--r--fs/squashfs/super.c3
3 files changed, 25 insertions, 4 deletions
diff --git a/fs/squashfs/fragment.c b/fs/squashfs/fragment.c
index 567093db587..bfd707569ab 100644
--- a/fs/squashfs/fragment.c
+++ b/fs/squashfs/fragment.c
@@ -71,9 +71,29 @@ int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
* Read the uncompressed fragment lookup table indexes off disk into memory
*/
__le64 *squashfs_read_fragment_index_table(struct super_block *sb,
- u64 fragment_table_start, unsigned int fragments)
+ u64 fragment_table_start, u64 next_table, unsigned int fragments)
{
unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
+ __le64 *table;
- return squashfs_read_table(sb, fragment_table_start, length);
+ /*
+ * Sanity check, length bytes should not extend into the next table -
+ * this check also traps instances where fragment_table_start is
+ * incorrectly larger than the next table start
+ */
+ if (fragment_table_start + length > next_table)
+ return ERR_PTR(-EINVAL);
+
+ table = squashfs_read_table(sb, fragment_table_start, length);
+
+ /*
+ * table[0] points to the first fragment table metadata block, this
+ * should be less than fragment_table_start
+ */
+ if (!IS_ERR(table) && table[0] >= fragment_table_start) {
+ kfree(table);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return table;
}
diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h
index 3b705f137eb..647b81b477d 100644
--- a/fs/squashfs/squashfs.h
+++ b/fs/squashfs/squashfs.h
@@ -57,7 +57,7 @@ extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64, u64,
/* fragment.c */
extern int squashfs_frag_lookup(struct super_block *, unsigned int, u64 *);
extern __le64 *squashfs_read_fragment_index_table(struct super_block *,
- u64, unsigned int);
+ u64, u64, unsigned int);
/* id.c */
extern int squashfs_get_id(struct super_block *, unsigned int, unsigned int *);
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 80a7119870a..efa8118260d 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -261,6 +261,7 @@ allocate_id_index_table:
msblk->inode_lookup_table = NULL;
goto failed_mount;
}
+ next_table = msblk->inode_lookup_table[0];
sb->s_export_op = &squashfs_export_ops;
@@ -278,7 +279,7 @@ handle_fragments:
/* Allocate and read fragment index table */
msblk->fragment_index = squashfs_read_fragment_index_table(sb,
- le64_to_cpu(sblk->fragment_table_start), fragments);
+ le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
if (IS_ERR(msblk->fragment_index)) {
ERROR("unable to read fragment index table\n");
err = PTR_ERR(msblk->fragment_index);