qga: handle possible SIGPIPE in guest-file-write

qemu-ga should not exit on guest-file-write to pipe without read end
but proper error code should be returned. The behavior of the
spawned process should be default thus SIGPIPE processing should be
reset to default after fork() but before exec().

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Yuri Pudgorodskiy <yur@virtuozzo.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

2 files changed, 23 insertions, 1 deletions

diff --git a/qga/commands.c b/qga/commands.c
index ced72d503e..68e8cfab18 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -225,6 +225,22 @@ static void guest_exec_child_watch(GPid pid, gint status, gpointer data)
     g_spawn_close_pid(pid);
 }
 
+/** Reset ignored signals back to default. */
+static void guest_exec_task_setup(gpointer data)
+{
+#if !defined(G_OS_WIN32)
+    struct sigaction sigact;
+
+    memset(&sigact, 0, sizeof(struct sigaction));
+    sigact.sa_handler = SIG_DFL;
+
+    if (sigaction(SIGPIPE, &sigact, NULL) != 0) {
+        slog("sigaction() failed to reset child process's SIGPIPE: %s",
+             strerror(errno));
+    }
+#endif
+}
+
 GuestExec *qmp_guest_exec(const char *path,
                        bool has_arg, strList *arg,
                        bool has_env, strList *env,
@@ -250,7 +266,7 @@ GuestExec *qmp_guest_exec(const char *path,
             G_SPAWN_SEARCH_PATH |
             G_SPAWN_DO_NOT_REAP_CHILD |
             G_SPAWN_STDOUT_TO_DEV_NULL | G_SPAWN_STDERR_TO_DEV_NULL,
-            NULL, NULL, &pid, NULL, NULL, NULL, &gerr);
+            guest_exec_task_setup, NULL, &pid, NULL, NULL, NULL, &gerr);
     if (!ret) {
         error_setg(err, QERR_QGA_COMMAND_FAILED, gerr->message);
         g_error_free(gerr);
diff --git a/qga/main.c b/qga/main.c
index aa6a063446..068169fcbc 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -161,6 +161,12 @@ static gboolean register_signal_handlers(void)
         g_error("error configuring signal handler: %s", strerror(errno));
     }
 
+    sigact.sa_handler = SIG_IGN;
+    if (sigaction(SIGPIPE, &sigact, NULL) != 0) {
+        g_error("error configuring SIGPIPE signal handler: %s",
+                strerror(errno));
+    }
+
     return true;
 }