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Commit 37986f63 authored by Phillip Lougher's avatar Phillip Lougher
Browse files

Squashfs: add sanity checks to id reading at mount time 



Fsfuzzer generates corrupted filesystems which throw a warn_on in
kmalloc.  One of these is due to a corrupted superblock no_ids 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 id table
structures.

Signed-off-by: default avatarPhillip Lougher <phillip@lougher.demon.co.uk>
parent 6f048645

fs/squashfs/id.c

+28 −2
Original line number Diff line number Diff line
@@ -66,11 +66,37 @@ int squashfs_get_id(struct super_block *sb, unsigned int index, 
 * Read uncompressed id lookup table indexes from disk into memory

 */

__le64 *squashfs_read_id_index_table(struct super_block *sb,

			u64 id_table_start, unsigned short no_ids)

		u64 id_table_start, u64 next_table, unsigned short no_ids)

{

	unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);

	__le64 *table;



	TRACE("In read_id_index_table, length %d\n", length);



	return squashfs_read_table(sb, id_table_start, length);

	/* Sanity check values */



	/* there should always be at least one id */

	if (no_ids == 0)

		return ERR_PTR(-EINVAL);



	/*

	 * length bytes should not extend into the next table - this check

	 * also traps instances where id_table_start is incorrectly larger

	 * than the next table start

	 */

	if (id_table_start + length > next_table)

		return ERR_PTR(-EINVAL);



	table = squashfs_read_table(sb, id_table_start, length);



	/*

	 * table[0] points to the first id lookup table metadata block, this

	 * should be less than id_table_start

	 */

	if (!IS_ERR(table) && table[0] >= id_table_start) {

		kfree(table);

		return ERR_PTR(-EINVAL);

	}



	return table;

}

fs/squashfs/squashfs.h

+1 −1
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ extern __le64 *squashfs_read_fragment_index_table(struct super_block *, 


/* id.c */

extern int squashfs_get_id(struct super_block *, unsigned int, unsigned int *);

extern __le64 *squashfs_read_id_index_table(struct super_block *, u64,

extern __le64 *squashfs_read_id_index_table(struct super_block *, u64, u64,

				unsigned short);



/* inode.c */

fs/squashfs/super.c

+7 −3
Original line number Diff line number Diff line
@@ -83,7 +83,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent) 
	long long root_inode;

	unsigned short flags;

	unsigned int fragments;

	u64 lookup_table_start, xattr_id_table_start;

	u64 lookup_table_start, xattr_id_table_start, next_table;

	int err;



	TRACE("Entered squashfs_fill_superblock\n");
@@ -217,8 +217,10 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent) 
	/* Handle xattrs */

	sb->s_xattr = squashfs_xattr_handlers;

	xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);

	if (xattr_id_table_start == SQUASHFS_INVALID_BLK)

	if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {

		next_table = msblk->bytes_used;

		goto allocate_id_index_table;

	}



	/* Allocate and read xattr id lookup table */

	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
@@ -230,11 +232,13 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent) 
		if (err != -ENOTSUPP)

			goto failed_mount;

	}

	next_table = msblk->xattr_table;



allocate_id_index_table:

	/* Allocate and read id index table */

	msblk->id_table = squashfs_read_id_index_table(sb,

		le64_to_cpu(sblk->id_table_start), le16_to_cpu(sblk->no_ids));

		le64_to_cpu(sblk->id_table_start), next_table,

		le16_to_cpu(sblk->no_ids));

	if (IS_ERR(msblk->id_table)) {

		ERROR("unable to read id index table\n");

		err = PTR_ERR(msblk->id_table);

fs/squashfs/xattr.h

+1 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ static inline __le64 *squashfs_read_xattr_id_table(struct super_block *sb, 
		u64 start, u64 *xattr_table_start, int *xattr_ids)

{

	ERROR("Xattrs in filesystem, these will be ignored\n");

	*xattr_table_start = start;

	return ERR_PTR(-ENOTSUPP);

}