Port: Add compat for platforms with no MSG_NOSIGNAL or SO_NOSIGPIPE

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/compat/socket.h b/src/common/compat/socket.h
index 5a6802aacd77720f72e7de93dfd4aeac61161b25..78610957b806e4c0d3e61d316a4e49baf649142e 100644 (file)
--- a/src/common/compat/socket.h
+++ b/src/common/compat/socket.h
@@ -23,6 +23,91 @@
 
 #include <common/macros.h>
 
+#ifndef MSG_NOSIGNAL
+# ifdef SO_NOSIGPIPE
+#   define MSG_NOSIGNAL SO_NOSIGPIPE
+# endif
+#endif
+
+#if defined(MSG_NOSIGNAL)
+static inline
+ssize_t lttng_recvmsg_nosigpipe(int sockfd, struct msghdr *msg)
+{
+       return recvmsg(sockfd, msg, MSG_NOSIGNAL);
+}
+#else
+
+#include <signal.h>
+#include <errno.h>
+
+static inline
+ssize_t lttng_recvmsg_nosigpipe(int sockfd, struct msghdr *msg)
+{
+       ssize_t received;
+       int saved_err;
+       sigset_t sigpipe_set, pending_set, old_set;
+       int sigpipe_was_pending;
+
+       /*
+        * Discard the SIGPIPE from send(), not disturbing any SIGPIPE
+        * that might be already pending. If a bogus SIGPIPE is sent to
+        * the entire process concurrently by a malicious user, it may
+        * be simply discarded.
+        */
+       if (sigemptyset(&pending_set)) {
+               return -1;
+       }
+       /*
+        * sigpending returns the mask of signals that are _both_
+        * blocked for the thread _and_ pending for either the thread or
+        * the entire process.
+        */
+       if (sigpending(&pending_set)) {
+               return -1;
+       }
+       sigpipe_was_pending = sigismember(&pending_set, SIGPIPE);
+       /*
+        * If sigpipe was pending, it means it was already blocked, so
+        * no need to block it.
+        */
+       if (!sigpipe_was_pending) {
+               if (sigemptyset(&sigpipe_set)) {
+                       return -1;
+               }
+               if (sigaddset(&sigpipe_set, SIGPIPE)) {
+                       return -1;
+               }
+               if (pthread_sigmask(SIG_BLOCK, &sigpipe_set, &old_set)) {
+                       return -1;
+               }
+       }
+
+       /* Send and save errno. */
+       received = recvmsg(sockfd, msg, 0);
+       saved_err = errno;
+
+       if (received == -1 && errno == EPIPE && !sigpipe_was_pending) {
+               struct timespec timeout = { 0, 0 };
+               int ret;
+
+               do {
+                       ret = sigtimedwait(&sigpipe_set, NULL,
+                               &timeout);
+               } while (ret == -1 && errno == EINTR);
+       }
+       if (!sigpipe_was_pending) {
+               if (pthread_sigmask(SIG_SETMASK, &old_set, NULL)) {
+                       return -1;
+               }
+       }
+       /* Restore send() errno */
+       errno = saved_err;
+
+       return received;
+}
+#endif
+
+
 #ifdef __linux__
 
 #define LTTNG_SOCK_CREDS SCM_CREDENTIALS

diff --git a/src/common/sessiond-comm/unix.c b/src/common/sessiond-comm/unix.c
index cf2c17ff7ad62444861d562cb9ec42c09d8e1077..5e0ba62812307d239a6d2f9db76475deb481a976 100644 (file)
--- a/src/common/sessiond-comm/unix.c
+++ b/src/common/sessiond-comm/unix.c
@@ -182,7 +182,7 @@ ssize_t lttcomm_recv_unix_sock(int sock, void *buf, size_t len)
 
        do {
                len_last = iov[0].iov_len;
-               ret = recvmsg(sock, &msg, MSG_NOSIGNAL);
+               ret = lttng_recvmsg_nosigpipe(sock, &msg);
                if (ret > 0) {
                        iov[0].iov_base += ret;
                        iov[0].iov_len -= ret;