[PATCH] xfs: validate acl count

[Christoph Hellwig]

This prevents in-memory corruption and possible panics if the on-disk
ACL is badly corrupted.

Signed-off-by: Christoph Hellwig <hch at lst.de>

Index: xfs/fs/xfs/xfs_acl.c
===================================================================
--- xfs.orig/fs/xfs/xfs_acl.c	2011-11-20 12:49:11.181244706 +0100
+++ xfs/fs/xfs/xfs_acl.c	2011-11-20 12:49:50.637697619 +0100
@@ -42,6 +42,8 @@ xfs_acl_from_disk(struct xfs_acl *aclp)
 	int count, i;
 
 	count = be32_to_cpu(aclp->acl_cnt);
+	if (count > XFS_ACL_MAX_ENTRIES)
+		return ERR_PTR(-EFSCORRUPTED);
 
 	acl = posix_acl_alloc(count, GFP_KERNEL);
 	if (!acl)