xfs: Validate the length of on-disk ACLs

In xfs_acl_from_disk, instead of trusting that xfs_acl.acl_cnt is correct,
make sure that the length of the attributes is correct as well.  Also, turn
the aclp parameter into a const pointer.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

2 files changed, 14 insertions, 7 deletions

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 9590a069e556..0e62682e7019 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -1487,9 +1487,13 @@ struct xfs_acl {
                                                 sizeof(struct xfs_acl_entry) \
                 : 25)
 
-#define XFS_ACL_MAX_SIZE(mp) \
+#define XFS_ACL_SIZE(cnt) \
         (sizeof(struct xfs_acl) + \
-                sizeof(struct xfs_acl_entry) * XFS_ACL_MAX_ENTRIES((mp)))
+                sizeof(struct xfs_acl_entry) * cnt)
+
+#define XFS_ACL_MAX_SIZE(mp) \
+        XFS_ACL_SIZE(XFS_ACL_MAX_ENTRIES((mp)))
+
 
 /* On-disk XFS extended attribute names */
 #define SGI_ACL_FILE            "SGI_ACL_FILE"
diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
index 4b641676f258..763e36560681 100644
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -37,16 +37,19 @@
 
 STATIC struct posix_acl *
 xfs_acl_from_disk(
-        struct xfs_acl  *aclp,
-        int             max_entries)
+        const struct xfs_acl    *aclp,
+        int                     len,
+        int                     max_entries)
 {
         struct posix_acl_entry *acl_e;
         struct posix_acl *acl;
-        struct xfs_acl_entry *ace;
+        const struct xfs_acl_entry *ace;
         unsigned int count, i;
 
+        if (len < sizeof(*aclp))
+                return ERR_PTR(-EFSCORRUPTED);
         count = be32_to_cpu(aclp->acl_cnt);
-        if (count > max_entries)
+        if (count > max_entries || XFS_ACL_SIZE(count) != len)
                 return ERR_PTR(-EFSCORRUPTED);
 
         acl = posix_acl_alloc(count, GFP_KERNEL);
@@ -163,7 +166,7 @@ xfs_get_acl(struct inode *inode, int type)
                 goto out;
         }
 
-        acl = xfs_acl_from_disk(xfs_acl, XFS_ACL_MAX_ENTRIES(ip->i_mount));
+        acl = xfs_acl_from_disk(xfs_acl, len, XFS_ACL_MAX_ENTRIES(ip->i_mount));
         if (IS_ERR(acl))
                 goto out;