From 08b0c891605acf727e43e3e03a25857d3e789b61 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 15 Aug 2019 11:30:50 +0300
Subject: [PATCH] drm/vmwgfx: Fix double free in vmw_recv_msg()
Git-commit: 08b0c891605acf727e43e3e03a25857d3e789b61
Patch-mainline: v5.3-rc8
References: bsc#1051510

We recently added a kfree() after the end of the loop:

	if (retries == RETRIES) {
		kfree(reply);
		return -EINVAL;
	}

There are two problems.  First the test is wrong and because retries
equals RETRIES if we succeed on the last iteration through the loop.
Second if we fail on the last iteration through the loop then the kfree
is a double free.

When you're reading this code, please note the break statement at the
end of the while loop.  This patch changes the loop so that if it's not
successful then "reply" is NULL and we can test for that afterward.

Cc: <stable@vger.kernel.org>
Fixes: 6b7c3b86f0b6 ("drm/vmwgfx: fix memory leak when too many retries have occurred")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/vmwgfx/vmwgfx_msg.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
index 59e9d05ab928..0af048d1a815 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg.c
@@ -353,7 +353,7 @@ static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
 				     !!(HIGH_WORD(ecx) & MESSAGE_STATUS_HB));
 		if ((HIGH_WORD(ebx) & MESSAGE_STATUS_SUCCESS) == 0) {
 			kfree(reply);
-
+			reply = NULL;
 			if ((HIGH_WORD(ebx) & MESSAGE_STATUS_CPT) != 0) {
 				/* A checkpoint occurred. Retry. */
 				continue;
@@ -377,7 +377,7 @@ static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
 
 		if ((HIGH_WORD(ecx) & MESSAGE_STATUS_SUCCESS) == 0) {
 			kfree(reply);
-
+			reply = NULL;
 			if ((HIGH_WORD(ecx) & MESSAGE_STATUS_CPT) != 0) {
 				/* A checkpoint occurred. Retry. */
 				continue;
@@ -389,10 +389,8 @@ static int vmw_recv_msg(struct rpc_channel *channel, void **msg,
 		break;
 	}
 
-	if (retries == RETRIES) {
-		kfree(reply);
+	if (!reply)
 		return -EINVAL;
-	}
 
 	*msg_len = reply_len;
 	*msg     = reply;
-- 
2.16.4