Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756816Ab1EYDUq (ORCPT ); Tue, 24 May 2011 23:20:46 -0400 Received: from anchor-post-3.mail.demon.net ([195.173.77.134]:54175 "EHLO anchor-post-3.mail.demon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753979Ab1EYDUp (ORCPT ); Tue, 24 May 2011 23:20:45 -0400 Date: Wed, 25 May 2011 04:20:42 +0100 From: Phillip Lougher To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 5/7] Squashfs: add sanity checks to lookup table reading at mount time Message-ID: <4ddc758a.DqyiUsz4x11Zbgnz%phillip@lougher.demon.co.uk> User-Agent: Heirloom mailx 12.4 7/29/08 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3525 Lines: 102 Fsfuzzer generates corrupted filesystems which throw a warn_on in kmalloc. One of these is due to a corrupted superblock inodes 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 lookup table structures. Signed-off-by: Phillip Lougher --- fs/squashfs/export.c | 29 +++++++++++++++++++++++++++-- fs/squashfs/squashfs.h | 2 +- fs/squashfs/super.c | 3 ++- 3 files changed, 30 insertions(+), 4 deletions(-) diff --git a/fs/squashfs/export.c b/fs/squashfs/export.c index cc6dd90..e54e4cb 100644 --- a/fs/squashfs/export.c +++ b/fs/squashfs/export.c @@ -121,13 +121,38 @@ static struct dentry *squashfs_get_parent(struct dentry *child) * Read uncompressed inode lookup table indexes off disk into memory */ __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, - u64 lookup_table_start, unsigned int inodes) + u64 lookup_table_start, u64 next_table, unsigned int inodes) { unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); + __le64 *table; TRACE("In read_inode_lookup_table, length %d\n", length); - return squashfs_read_table(sb, lookup_table_start, length); + /* Sanity check values */ + + /* there should always be at least one inode */ + if (inodes == 0) + return ERR_PTR(-EINVAL); + + /* length bytes should not extend into the next table - this check + * also traps instances where lookup_table_start is incorrectly larger + * than the next table start + */ + if (lookup_table_start + length > next_table) + return ERR_PTR(-EINVAL); + + table = squashfs_read_table(sb, lookup_table_start, length); + + /* + * table[0] points to the first inode lookup table metadata block, + * this should be less than lookup_table_start + */ + if (table[0] >= lookup_table_start) { + kfree(table); + return ERR_PTR(-EINVAL); + } + + return table; } diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h index 0e3d220..3b705f1 100644 --- a/fs/squashfs/squashfs.h +++ b/fs/squashfs/squashfs.h @@ -51,7 +51,7 @@ extern const struct squashfs_decompressor *squashfs_lookup_decompressor(int); extern void *squashfs_decompressor_init(struct super_block *, unsigned short); /* export.c */ -extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64, +extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64, u64, unsigned int); /* fragment.c */ diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c index 8f5f278..80a7119 100644 --- a/fs/squashfs/super.c +++ b/fs/squashfs/super.c @@ -245,6 +245,7 @@ allocate_id_index_table: msblk->id_table = NULL; goto failed_mount; } + next_table = msblk->id_table[0]; /* Handle inode lookup table */ lookup_table_start = le64_to_cpu(sblk->lookup_table_start); @@ -253,7 +254,7 @@ allocate_id_index_table: /* Allocate and read inode lookup table */ msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb, - lookup_table_start, msblk->inodes); + lookup_table_start, next_table, msblk->inodes); if (IS_ERR(msblk->inode_lookup_table)) { ERROR("unable to read inode lookup table\n"); err = PTR_ERR(msblk->inode_lookup_table); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/