[PATCH v3 0/2] Vhost: fix FD leaks and improve logs

[PATCH v3 0/2] Vhost: fix FD leaks and improve logs

[Maxime Coquelin]

This two-patches series fix possible FD leaks when
receiving Vhost-user messages fails. It also improve
logging by differentiating message's buffer truncation
and control data truncation.

Changes in v3:
==============
- Improve logs on error (David)

Maxime Coquelin (2):
  vhost: fix possible FDs leak
  vhost: fix possible FD leaks on truncation

 lib/vhost/socket.c     |  8 +++++---
 lib/vhost/vhost_user.c | 40 ++++++++++++++++++++++++++--------------
 2 files changed, 31 insertions(+), 17 deletions(-)

-- 
2.39.1

[PATCH v3 1/2] vhost: fix possible FDs leak

[Maxime Coquelin]

On failure, read_vhost_message() only closed the message
FDs if the header size was unexpected, but there are other
cases where it is required. For exemple in the case the
payload size read from the header is greater than the
expected maximum payload size.

This patch fixes this by closing all messages FDs in all
error cases. It also improve error logging by displaying
the request name when failure happens if possible.

Fixes: bf472259dde6 ("vhost: fix possible denial of service by leaking FDs")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
---
 lib/vhost/vhost_user.c | 40 ++++++++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
index 8f33d5f4d9..a6d8269d91 100644
--- a/lib/vhost/vhost_user.c
+++ b/lib/vhost/vhost_user.c
@@ -2827,29 +2827,36 @@ read_vhost_message(struct virtio_net *dev, int sockfd, struct  vhu_msg_context *
 
 	ret = read_fd_message(dev->ifname, sockfd, (char *)&ctx->msg, VHOST_USER_HDR_SIZE,
 		ctx->fds, VHOST_MEMORY_MAX_NREGIONS, &ctx->fd_num);
-	if (ret <= 0) {
-		return ret;
-	} else if (ret != VHOST_USER_HDR_SIZE) {
+	if (ret <= 0)
+		goto out;
+
+	if (ret != VHOST_USER_HDR_SIZE) {
 		VHOST_LOG_CONFIG(dev->ifname, ERR, "Unexpected header size read\n");
-		close_msg_fds(ctx);
-		return -1;
+		ret = -1;
+		goto out;
 	}
 
 	if (ctx->msg.size) {
 		if (ctx->msg.size > sizeof(ctx->msg.payload)) {
 			VHOST_LOG_CONFIG(dev->ifname, ERR, "invalid msg size: %d\n",
 				ctx->msg.size);
-			return -1;
+			ret = -1;
+			goto out;
 		}
 		ret = read(sockfd, &ctx->msg.payload, ctx->msg.size);
 		if (ret <= 0)
-			return ret;
+			goto out;
 		if (ret != (int)ctx->msg.size) {
 			VHOST_LOG_CONFIG(dev->ifname, ERR, "read control message failed\n");
-			return -1;
+			ret = -1;
+			goto out;
 		}
 	}
 
+out:
+	if (ret <= 0)
+		close_msg_fds(ctx);
+
 	return ret;
 }
 
@@ -2997,13 +3004,10 @@ vhost_user_msg_handler(int vid, int fd)
 		}
 	}
 
+	ctx.msg.request.master = VHOST_USER_NONE;
 	ret = read_vhost_message(dev, fd, &ctx);
-	if (ret <= 0) {
-		if (ret < 0)
-			VHOST_LOG_CONFIG(dev->ifname, ERR, "vhost read message failed\n");
-		else
-			VHOST_LOG_CONFIG(dev->ifname, INFO, "vhost peer closed\n");
-
+	if (ret == 0) {
+		VHOST_LOG_CONFIG(dev->ifname, INFO, "vhost peer closed\n");
 		return -1;
 	}
 
@@ -3013,6 +3017,14 @@ vhost_user_msg_handler(int vid, int fd)
 	else
 		msg_handler = NULL;
 
+	if (ret < 0) {
+		VHOST_LOG_CONFIG(dev->ifname, ERR, "vhost read message %s%s%sfailed\n",
+				msg_handler != NULL ? "for " : "",
+				msg_handler != NULL ? msg_handler->description : "",
+				msg_handler != NULL ? " " : "");
+		return -1;
+	}
+
 	if (msg_handler != NULL && msg_handler->description != NULL) {
 		if (request != VHOST_USER_IOTLB_MSG)
 			VHOST_LOG_CONFIG(dev->ifname, INFO,
-- 
2.39.1

[PATCH v3 2/2] vhost: fix possible FD leaks on truncation

[Maxime Coquelin]

This patch fixes possible FDs leaks when truncation happens
on either the message buffer or its control data. Indeed,
by returning early, it did not let a chance to retrieve the
FDs passed as ancillary data, and so caused a potential FDs
leak.

This patch fixes this by extracting the FDs from the
ancillary data as long as recvmsg() call succeeded. It also
improves the logs to differentiate between MSG_TRUNC and
MSG_CTRUNC.

Fixes: bf472259dde6 ("vhost: fix possible denial of service by leaking FDs")
Cc: stable@dpdk.org

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
---
 lib/vhost/socket.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index 863a6f6d52..669c322e12 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -129,10 +129,12 @@ read_fd_message(char *ifname, int sockfd, char *buf, int buflen, int *fds, int m
 		return ret;
 	}
 
-	if (msgh.msg_flags & (MSG_TRUNC | MSG_CTRUNC)) {
+	if (msgh.msg_flags & MSG_TRUNC)
 		VHOST_LOG_CONFIG(ifname, ERR, "truncated msg (fd %d)\n", sockfd);
-		return -1;
-	}
+
+	/* MSG_CTRUNC may be caused by LSM misconfiguration */
+	if (msgh.msg_flags & MSG_CTRUNC)
+		VHOST_LOG_CONFIG(ifname, ERR, "truncated control data (fd %d)\n", sockfd);
 
 	for (cmsg = CMSG_FIRSTHDR(&msgh); cmsg != NULL;
 		cmsg = CMSG_NXTHDR(&msgh, cmsg)) {
-- 
2.39.1

Re: [PATCH v3 0/2] Vhost: fix FD leaks and improve logs

[Maxime Coquelin]

On 2/7/23 17:22, Maxime Coquelin wrote:
> This two-patches series fix possible FD leaks when
> receiving Vhost-user messages fails. It also improve
> logging by differentiating message's buffer truncation
> and control data truncation.
> 
> Changes in v3:
> ==============
> - Improve logs on error (David)
> 
> Maxime Coquelin (2):
>    vhost: fix possible FDs leak
>    vhost: fix possible FD leaks on truncation
> 
>   lib/vhost/socket.c     |  8 +++++---
>   lib/vhost/vhost_user.c | 40 ++++++++++++++++++++++++++--------------
>   2 files changed, 31 insertions(+), 17 deletions(-)
> 


Applied to dpdk-next-virtio/main.

Thanks,
Maxime