linux-kernel - [PATCH 1/1] Fix: vmw_vmci driver get_user_pages

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Message-Id: <20171031230038.7476-1-mathieu.desnoyers@efficios.com>
Date:   Tue, 31 Oct 2017 19:00:38 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        George Zhang <georgezhang@...are.com>,
        Andy king <acking@...are.com>,
        Dmitry Torokhov <dtor@...are.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH 1/1] Fix: vmw_vmci driver get_user_pages_fast error handling

Comparing a signed return value against an unsigned num_pages
field performs the comparison as "unsigned", and therefore mistakenly
considers get_user_pages_fast() errors as success.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: Alexander Viro <viro@...iv.linux.org.uk>
CC: George Zhang <georgezhang@...are.com>
CC: Andy king <acking@...are.com>
CC: Dmitry Torokhov <dtor@...are.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: linux-fsdevel@...r.kernel.org
---
 drivers/misc/vmw_vmci/vmci_queue_pair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/vmw_vmci/vmci_queue_pair.c b/drivers/misc/vmw_vmci/vmci_queue_pair.c
index 8af5c2672f71..f71db848ce81 100644
--- a/drivers/misc/vmw_vmci/vmci_queue_pair.c
+++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c
@@ -755,7 +755,7 @@ static int qp_host_get_user_memory(u64 produce_uva,
 	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 < 0 || retval < produce_q->kernel_if->num_pages) {
 		pr_debug("get_user_pages_fast(produce) failed (retval=%d)",
 			retval);
 		qp_release_pages(produce_q->kernel_if->u.h.header_page,
@@ -767,7 +767,7 @@ static int qp_host_get_user_memory(u64 produce_uva,
 	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 < 0 || retval < consume_q->kernel_if->num_pages) {
 		pr_debug("get_user_pages_fast(consume) failed (retval=%d)",
 			retval);
 		qp_release_pages(consume_q->kernel_if->u.h.header_page,
-- 
2.11.0