On 1/27/23 14:57, Maxime Coquelin wrote:
This patch improves truncated messages logging to ease debugging. First, it differentiates between message's buffer truncation and control data truncation. Indeed, MSG_CTRUNC can happen even if enough room was provided, in case LSM detects access rights issue. Then, it does not return directly in case of truncation, but returns normally to let a chance to display request type in Vhost-user protocol layer logs. Signed-off-by: Maxime Coquelin <[email protected]> --- lib/vhost/socket.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
Discussing with David, there was/is a possible FDs leak when truncation happens, a V2 is coming to handle these properly.
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)) {
