linux-kernel - [PATCH] VMCI: Fix NULL pointer dereference on context ptr

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Date:   Tue, 17 Mar 2020 14:29:57 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Xin Tan <tanxin.ctf@...il.com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Vishnu DASA <vdasa@...are.com>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Thomas Gleixner <tglx@...utronix.de>,
        Allison Randal <allison@...utok.net>,
        Ira Weiny <ira.weiny@...el.com>,
        Mike Marshall <hubcap@...ibond.com>,
        linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, kjlu@....edu
Subject: [PATCH] VMCI: Fix NULL pointer dereference on context ptr

The refcount wrapper function vmci_ctx_get() may return NULL
context ptr. Thus, we need to add a NULL pointer check
before its dereference.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 drivers/misc/vmw_vmci/vmci_context.c    |  2 ++
 drivers/misc/vmw_vmci/vmci_queue_pair.c | 17 +++++++++++------
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/vmw_vmci/vmci_context.c b/drivers/misc/vmw_vmci/vmci_context.c
index 16695366ec92..a20878fba374 100644
--- a/drivers/misc/vmw_vmci/vmci_context.c
+++ b/drivers/misc/vmw_vmci/vmci_context.c
@@ -898,6 +898,8 @@ void vmci_ctx_rcv_notifications_release(u32 context_id,
 					bool success)
 {
 	struct vmci_ctx *context = vmci_ctx_get(context_id);
+	if (context == NULL)
+		return;
 
 	spin_lock(&context->lock);
 	if (!success) {
diff --git a/drivers/misc/vmw_vmci/vmci_queue_pair.c b/drivers/misc/vmw_vmci/vmci_queue_pair.c
index 8531ae781195..2ecb22d08692 100644
--- a/drivers/misc/vmw_vmci/vmci_queue_pair.c
+++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c
@@ -1575,11 +1575,14 @@ static int qp_broker_attach(struct qp_broker_entry *entry,
 		 */
 
 		create_context = vmci_ctx_get(entry->create_id);
-		supports_host_qp = vmci_ctx_supports_host_qp(create_context);
-		vmci_ctx_put(create_context);
+		if (!create_context) {
+			supports_host_qp =
+				vmci_ctx_supports_host_qp(create_context);
+			vmci_ctx_put(create_context);
 
-		if (!supports_host_qp)
-			return VMCI_ERROR_INVALID_RESOURCE;
+			if (!supports_host_qp)
+				return VMCI_ERROR_INVALID_RESOURCE;
+		}
 	}
 
 	if ((entry->qp.flags & ~VMCI_QP_ASYMM) != (flags & ~VMCI_QP_ASYMM_PEER))
@@ -1808,7 +1811,8 @@ static int qp_alloc_host_work(struct vmci_handle *handle,
 		pr_devel("queue pair broker failed to alloc (result=%d)\n",
 			 result);
 	}
-	vmci_ctx_put(context);
+	if (context)
+		vmci_ctx_put(context);
 	return result;
 }
 
@@ -1859,7 +1863,8 @@ static int qp_detatch_host_work(struct vmci_handle handle)
 
 	result = vmci_qp_broker_detach(handle, context);
 
-	vmci_ctx_put(context);
+	if (context)
+		vmci_ctx_put(context);
 	return result;
 }
 
-- 
2.7.4