job-control: set CLOEXEC on pty processes. #5986

Before this change, new processes started with libuv prevented SIGHUP
from reaching pty processes (by keeping the ptmx file descriptor open).

2 files changed, 48 insertions, 2 deletions

diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index e930561234..af60e1b7af 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -391,6 +391,35 @@ int os_open(const char* path, int flags, int mode)
   return r;
 }
 
+/// Sets file descriptor `fd` to close-on-exec.
+//
+// @return -1 if failed to set, 0 otherwise.
+int os_set_cloexec(const int fd)
+{
+#ifdef HAVE_FD_CLOEXEC
+  int e;
+  int fdflags = fcntl(fd, F_GETFD);
+  if (fdflags < 0) {
+    e = errno;
+    ELOG("Failed to get flags on descriptor %d: %s", fd, strerror(e));
+    errno = e;
+    return -1;
+  }
+  if ((fdflags & FD_CLOEXEC) == 0
+      && fcntl(fd, F_SETFD, fdflags | FD_CLOEXEC) < 0) {
+    e = errno;
+    ELOG("Failed to set CLOEXEC on descriptor %d: %s", fd, strerror(e));
+    errno = e;
+    return -1;
+  }
+  return 0;
+#endif
+
+  // No FD_CLOEXEC flag. On Windows, the file should have been opened with
+  // O_NOINHERIT anyway.
+  return -1;
+}
+
 /// Close a file
 ///
 /// @return 0 or libuv error code on failure.
diff --git a/src/nvim/os/pty_process_unix.c b/src/nvim/os/pty_process_unix.c
index f5ba0c2612..71a5e13de5 100644
--- a/src/nvim/os/pty_process_unix.c
+++ b/src/nvim/os/pty_process_unix.c
@@ -73,6 +73,13 @@ int pty_process_spawn(PtyProcess *ptyproc)
     goto error;
   }
 
+  // Other jobs and providers should not get a copy of this file descriptor.
+  if (os_set_cloexec(master) == -1) {
+    status = -errno;
+    ELOG("Failed to set CLOEXEC on ptmx file descriptor");
+    goto error;
+  }
+
   if (proc->in
       && (status = set_duplicating_descriptor(master, &proc->in->uv.pipe))) {
     goto error;
@@ -215,14 +222,24 @@ static int set_duplicating_descriptor(int fd, uv_pipe_t *pipe)
     ELOG("Failed to dup descriptor %d: %s", fd, strerror(errno));
     return status;
   }
+
+  if (os_set_cloexec(fd_dup) == -1) {
+    status = -errno;
+    ELOG("Failed to set CLOEXEC on duplicate fd");
+    goto error;
+  }
+
   status = uv_pipe_open(pipe, fd_dup);
   if (status) {
     ELOG("Failed to set pipe to descriptor %d: %s",
          fd_dup, uv_strerror(status));
-    close(fd_dup);
-    return status;
+    goto error;
   }
   return status;
+
+error:
+  close(fd_dup);
+  return status;
 }
 
 static void chld_handler(uv_signal_t *handle, int signum)