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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: Phillip Lougher <phillip@lougher.demon.co.uk>
This commit is contained in:
Phillip Lougher 2011-05-24 04:05:22 +01:00
parent 6f04864515
commit 37986f63c8
4 changed files with 37 additions and 6 deletions
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30
fs/squashfs/id.c
View File

@ -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;
}

2
fs/squashfs/squashfs.h
View File

@ -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 */

10
fs/squashfs/super.c
View File

@ -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);

1
fs/squashfs/xattr.h
View File

@ -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);
}