Re: [patch] fs: NULL dereference in posix_acl_to_xattr()

Steven Whitehouse
2014-02-17T10:16:21Z

Hi,

On Fri, 2014-02-14 at 12:05 +0300, Dan Carpenter wrote:
> This patch moves the dereference of "buffer" after the check for NULL.
> The only place which passes a NULL parameter is gfs2_set_acl().
>
> Cc: stable <stable@vger.kernel.org>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>

Al, are you going to take this, or should I put it through the GFS2 tree
instead?

I also wonder whether GFS2 should be calling posix_acl_xattr_size() like
the other filesystems, or whether in fact calling posix_acl_to_xattr()
with a NULL buffer is still accepted usage here?

Steve.

> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 11c54fd51e16..9e363e41dacc 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -723,7 +723,7 @@ posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
> void *buffer, size_t size)
> {
> posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
> - posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
> + posix_acl_xattr_entry *ext_entry;
> int real_size, n;
>
> real_size = posix_acl_xattr_size(acl->a_count);
> @@ -731,7 +731,8 @@ posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
> return real_size;
> if (real_size > size)
> return -ERANGE;
> -
> +
> + ext_entry = ext_acl->a_entries;
> ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);
>
> for (n=0; n < acl->a_count; n++, ext_entry++) {