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Subject[PATCH 1/1] squashfs: harden sanity check in squashfs_read_xattr_id_table
Date
While mounting a corrupted filesystem, a signed integer '*xattr_ids' can
become less than zero. This leads to the incorrect computation of 'len'
and 'indexes' values which can cause null-ptr-deref in copy_bio_to_actor()
or out-of-bounds accesses in the next sanity checks inside
squashfs_read_xattr_id_table().

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 506220d2ba21 ("squashfs: add more sanity checks in xattr id lookup")
Reported-by: syzbot+082fa4af80a5bb1a9843@syzkaller.appspotmail.com
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
fs/squashfs/xattr_id.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/squashfs/xattr_id.c b/fs/squashfs/xattr_id.c
index 087cab8c78f4..f6d78cbc3e74 100644
--- a/fs/squashfs/xattr_id.c
+++ b/fs/squashfs/xattr_id.c
@@ -76,7 +76,7 @@ __le64 *squashfs_read_xattr_id_table(struct super_block *sb, u64 table_start,
/* Sanity check values */

/* there is always at least one xattr id */
- if (*xattr_ids == 0)
+ if (*xattr_ids <= 0)
return ERR_PTR(-EINVAL);

len = SQUASHFS_XATTR_BLOCK_BYTES(*xattr_ids);
--
2.34.1
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