[PATCH 3.14 29/33] pstore: skip zero size persistent ram buffer in traverse

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liu ShuoX <shuox.liu@intel.com>

commit aa9a4a1edfbd3d223af01db833da2f07850bc655 upstream.

In ramoops_pstore_read, a valid prz pointer with zero size buffer will
break traverse of all persistent ram buffers.  The latter buffer might be
lost.

Signed-off-by: Liu ShuoX <shuox.liu@intel.com>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Cc: Colin Cross <ccross@android.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: HuKeping <hukeping@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/pstore/ram.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -126,12 +126,12 @@ ramoops_get_next_prz(struct persistent_r
 
 	prz = przs[i];
 
-	if (update) {
-		/* Update old/shadowed buffer. */
+	/* Update old/shadowed buffer. */
+	if (update)
 		persistent_ram_save_old(prz);
-		if (!persistent_ram_old_size(prz))
-			return NULL;
-	}
+
+	if (!persistent_ram_old_size(prz))
+		return NULL;
 
 	*typep = type;
 	*id = i;