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Squashfs: add sanity checks to fragment reading at mount time 

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

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
This commit is contained in:
Phillip Lougher 2011-05-24 04:33:34 +01:00
parent ac51a0a713
commit 1cac63cc9b
3 changed files with 25 additions and 4 deletions
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24
fs/squashfs/fragment.c
View File

@ -71,9 +71,29 @@ int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
* Read the uncompressed fragment lookup table indexes off disk into memory
*/
__le64 *squashfs_read_fragment_index_table(struct super_block *sb,
u64 fragment_table_start, unsigned int fragments)
u64 fragment_table_start, u64 next_table, unsigned int fragments)
{
unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
__le64 *table;
return squashfs_read_table(sb, fragment_table_start, length);
/*
* Sanity check, length bytes should not extend into the next table -
* this check also traps instances where fragment_table_start is
* incorrectly larger than the next table start
*/
if (fragment_table_start + length > next_table)
return ERR_PTR(-EINVAL);
table = squashfs_read_table(sb, fragment_table_start, length);
/*
* table[0] points to the first fragment table metadata block, this
* should be less than fragment_table_start
*/
if (!IS_ERR(table) && table[0] >= fragment_table_start) {
kfree(table);
return ERR_PTR(-EINVAL);
}
return table;
}

2
fs/squashfs/squashfs.h
View File

@ -57,7 +57,7 @@ extern __le64 *squashfs_read_inode_lookup_table(struct super_block *, u64, u64,
/* fragment.c */
extern int squashfs_frag_lookup(struct super_block *, unsigned int, u64 *);
extern __le64 *squashfs_read_fragment_index_table(struct super_block *,
u64, unsigned int);
u64, u64, unsigned int);
/* id.c */
extern int squashfs_get_id(struct super_block *, unsigned int, unsigned int *);

3
fs/squashfs/super.c
View File

@ -261,6 +261,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
msblk->inode_lookup_table = NULL;
goto failed_mount;
}
next_table = msblk->inode_lookup_table[0];
sb->s_export_op = &squashfs_export_ops;
@ -278,7 +279,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
/* Allocate and read fragment index table */
msblk->fragment_index = squashfs_read_fragment_index_table(sb,
le64_to_cpu(sblk->fragment_table_start), fragments);
le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
if (IS_ERR(msblk->fragment_index)) {
ERROR("unable to read fragment index table\n");
err = PTR_ERR(msblk->fragment_index);