fs/posix_acl.c: make posix_acl_create() safer and cleaner

If posix_acl_create() returns an error code then "*acl" and "*default_acl"
can be uninitialized or point to freed memory.  This is a dangerous thing
to do.  For example, it causes a problem in ocfs2_reflink():

	fs/ocfs2/refcounttree.c:4327 ocfs2_reflink()
	error: potentially using uninitialized 'default_acl'.

I've re-written this so we set the pointers to NULL at the start.  I've
added a temporary "clone" variable to hold the value of "*acl" until end.
Setting them to NULL means means we don't need the "no_acl" label.  We may
as well remove the "apply_umask" stuff forward and remove that label as
well.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 84bb65b835701365126833a9e74d9e5d7a8a6c00..4fb17ded7d4780d8d19e7c68cb1c7cedfeb79cf7 100644 (file)
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -547,51 +547,45 @@ posix_acl_create(struct inode *dir, umode_t *mode,
                struct posix_acl **default_acl, struct posix_acl **acl)
 {
        struct posix_acl *p;
+       struct posix_acl *clone;
        int ret;
 
+       *acl = NULL;
+       *default_acl = NULL;
+
        if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
-               goto no_acl;
+               return 0;
 
        p = get_acl(dir, ACL_TYPE_DEFAULT);
-       if (IS_ERR(p)) {
-               if (p == ERR_PTR(-EOPNOTSUPP))
-                       goto apply_umask;
-               return PTR_ERR(p);
+       if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
+               *mode &= ~current_umask();
+               return 0;
        }
+       if (IS_ERR(p))
+               return PTR_ERR(p);
 
-       if (!p)
-               goto apply_umask;
-
-       *acl = posix_acl_clone(p, GFP_NOFS);
-       if (!*acl)
+       clone = posix_acl_clone(p, GFP_NOFS);
+       if (!clone)
                goto no_mem;
 
-       ret = posix_acl_create_masq(*acl, mode);
+       ret = posix_acl_create_masq(clone, mode);
        if (ret < 0)
                goto no_mem_clone;
 
-       if (ret == 0) {
-               posix_acl_release(*acl);
-               *acl = NULL;
-       }
+       if (ret == 0)
+               posix_acl_release(clone);
+       else
+               *acl = clone;
 
-       if (!S_ISDIR(*mode)) {
+       if (!S_ISDIR(*mode))
                posix_acl_release(p);
-               *default_acl = NULL;
-       } else {
+       else
                *default_acl = p;
-       }
-       return 0;
 
-apply_umask:
-       *mode &= ~current_umask();
-no_acl:
-       *default_acl = NULL;
-       *acl = NULL;
        return 0;
 
 no_mem_clone:
-       posix_acl_release(*acl);
+       posix_acl_release(clone);
 no_mem:
        posix_acl_release(p);
        return -ENOMEM;