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[82.51.6.75]) by smtp.gmail.com with ESMTPSA id w10sm34795307wra.34.2020.11.18.06.37.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Nov 2020 06:37:45 -0800 (PST) From: "Andrea Parri (Microsoft)" To: linux-kernel@vger.kernel.org Cc: "K . Y . Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , linux-hyperv@vger.kernel.org, Michael Kelley , Juan Vazquez , Saruhan Karademir , "Andrea Parri (Microsoft)" Subject: [PATCH 4/6] Drivers: hv: vmbus: Avoid use-after-free in vmbus_onoffer_rescind() Date: Wed, 18 Nov 2020 15:36:47 +0100 Message-Id: <20201118143649.108465-5-parri.andrea@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201118143649.108465-1-parri.andrea@gmail.com> References: <20201118143649.108465-1-parri.andrea@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When channel->device_obj is non-NULL, vmbus_onoffer_rescind() could invoke put_device(), that will eventually release the device and free the channel object (cf. vmbus_device_release()). However, a pointer to the object is dereferenced again later to load the primary_channel. The use-after-free can be avoided by noticing that this load/check is redundant if device_obk is non-NULL: primary_channel must be NULL if device_obj is non-NULL, cf. vmbus_add_channel_work(). Reported-by: Juan Vazquez Signed-off-by: Andrea Parri (Microsoft) --- drivers/hv/channel_mgmt.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 5bc5eef5da159..4072fd1f22146 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -1116,8 +1116,7 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) vmbus_device_unregister(channel->device_obj); put_device(dev); } - } - if (channel->primary_channel != NULL) { + } else if (channel->primary_channel != NULL) { /* * Sub-channel is being rescinded. Following is the channel * close sequence when initiated from the driveri (refer to -- 2.25.1