linux-kernel - [PATCH 3.16 030/328] vmci: type promotion bug in qp_host_get_user

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Message-ID: <lsq.1544392233.53554730@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: [PATCH 3.16 030/328] vmci: type promotion bug in qp_host_get_user_memory()

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Dan Carpenter <dan.carpenter@...cle.com>

commit 7fb2fd4e25fc1fb10dcb30b5519de257cfeae84c upstream.

The problem is that if get_user_pages_fast() fails and returns a
negative error code, it gets type promoted to a high positive value and
treated as a success.

Fixes: 06164d2b72aa ("VMCI: queue pairs implementation.")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/misc/vmw_vmci/vmci_queue_pair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/misc/vmw_vmci/vmci_queue_pair.c
+++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c
@@ -735,7 +735,7 @@ static int qp_host_get_user_memory(u64 p
 	retval = get_user_pages_fast((uintptr_t) produce_uva,
 				     produce_q->kernel_if->num_pages, 1,
 				     produce_q->kernel_if->u.h.header_page);
-	if (retval < produce_q->kernel_if->num_pages) {
+	if (retval < (int)produce_q->kernel_if->num_pages) {
 		pr_warn("get_user_pages(produce) failed (retval=%d)", retval);
 		qp_release_pages(produce_q->kernel_if->u.h.header_page,
 				 retval, false);
@@ -746,7 +746,7 @@ static int qp_host_get_user_memory(u64 p
 	retval = get_user_pages_fast((uintptr_t) consume_uva,
 				     consume_q->kernel_if->num_pages, 1,
 				     consume_q->kernel_if->u.h.header_page);
-	if (retval < consume_q->kernel_if->num_pages) {
+	if (retval < (int)consume_q->kernel_if->num_pages) {
 		pr_warn("get_user_pages(consume) failed (retval=%d)", retval);
 		qp_release_pages(consume_q->kernel_if->u.h.header_page,
 				 retval, false);