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Squashfs: add sanity checks to lookup table reading at mount time 

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 <phillip@lougher.demon.co.uk>
This commit is contained in:
Phillip Lougher 2011-05-24 04:15:21 +01:00
parent 37986f63c8
commit ac51a0a713
3 changed files with 30 additions and 4 deletions
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29
fs/squashfs/export.c
View File

@ -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 (!IS_ERR(table) && table[0] >= lookup_table_start) {
kfree(table);
return ERR_PTR(-EINVAL);
}
return table;
}

2
fs/squashfs/squashfs.h
View File

@ -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 */

3
fs/squashfs/super.c
View File

@ -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);