From 1cac63cc9b2ff0d16ab2d16232b1a6ee8676a47b Mon Sep 17 00:00:00 2001 From: Phillip Lougher Date: Tue, 24 May 2011 04:33:34 +0100 Subject: 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 --- fs/squashfs/fragment.c | 24 ++++++++++++++++++++++-- fs/squashfs/squashfs.h | 2 +- fs/squashfs/super.c | 3 ++- 3 files changed, 25 insertions(+), 4 deletions(-) diff --git a/fs/squashfs/fragment.c b/fs/squashfs/fragment.c index 567093db5870..bfd707569ab7 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 3b705f137ebb..647b81b477d4 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 80a7119870a6..efa8118260d4 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); -- cgit v1.2.3