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Squashfs: add sanity checks to id reading at mount time

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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
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@@ -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;
}