[Qemu-devel] [PATCH 4/6] qga: handle possible SIGPIPE in guest-file-write

["Denis V. Lunev" <den@openvz.org>]

From: Olga Krishtal <okrishtal@parallels.com>

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: Olga Krishtal <okristal@parallels.com>
Acked-by: Roman Kagan <rkagan@parallels.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 qga/commands-posix.c | 16 ++++++++++++++++
 qga/main.c           |  6 ++++++
 2 files changed, 22 insertions(+)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index aa11932..64d9b2d 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -961,6 +961,20 @@ static int guest_exec_set_std(GuestFileHandle *gfh, int std_fd, int fd_null)
     return 0;
 }
 
+/** Reset ignored signals back to default. */
+static void guest_exec_reset_child_sig(void)
+{
+    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));
+    }
+}
+
 GuestExec *qmp_guest_exec(const char *path,
                        bool has_params, strList *params,
                        bool has_env, strList *env,
@@ -1032,6 +1046,8 @@ GuestExec *qmp_guest_exec(const char *path,
             /* exit(1); */
         }
 
+        guest_exec_reset_child_sig();
+
         execvpe(path, (char * const *)argv, (char * const *)envp);
         slog("guest-exec child failed: %s", strerror(errno));
         exit(1);
diff --git a/qga/main.c b/qga/main.c
index 9939a2b..bc6414c 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -160,6 +160,12 @@ 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;
 }
 
-- 
1.9.1