Hi, Dan,
On Sat, Jan 24, 2015 at 10:31:24PM +0300, Dan Carpenter wrote:
> If posix_acl_create() returns an error code then "*acl" and
> "*default_acl" can be uninitialized or point to freed memory. This
> causes problems in some of the callers where it is expected that they
> are NULL on error. For example, ocfs2_reflink() has a bug.
>
> fs/ocfs2/refcounttree.c:4329 ocfs2_reflink()
> error: potentially using uninitialized 'default_acl'.
>
> I have re-written this function and re-arranged things so that they are
> set to NULL at the start and then only set to a valid pointer at the end
> of the function.
>
I'm inclined to blame ocfs2 and not posix_acl_create() here. I'd imagine
that most C programmers' intuition is generally not to trust any return
parameters when the return value is an error. Accordingly, a quick scan
of the tree showed that all of the other users of posix_acl_create() are
doing it correctly and only calling posix_acl_release() when it returns
success.
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 0855f77..66d2c13 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -546,50 +546,43 @@ int
> 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 *p, *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)
> return -ENOMEM;
>
> - ret = posix_acl_create_masq(*acl, mode);
> + ret = posix_acl_create_masq(clone, mode);
> if (ret < 0) {
> - posix_acl_release(*acl);
> + posix_acl_release(clone);
> return -ENOMEM;
> }
>
> - 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;
> }
> EXPORT_SYMBOL_GPL(posix_acl_create);
> --
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--
Omar
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