libselinux: always set errno on context translation failure

Allow callers to expect errno is set on failure, e.g. other exported
libselinux functions like setexecfilecon(3).

Signed-off-by: Christian Göttsche <[email protected]>
Acked-by: James Carter <[email protected]>

libselinux/src/setrans_client.c

@@ -92,8 +92,10 @@ send_request(int fd, uint32_t function, const char *data1, const char *data2)
  ssize_t count, expected;
  unsigned int i;
 
- if (fd < 0)
+ if (fd < 0) {
+ errno = EINVAL;
  return -1;
+ }
 
  if (!data1)
  data1 = "";
@@ -123,8 +125,12 @@ send_request(int fd, uint32_t function, const char *data1, const char *data2)
 
  while (((count = sendmsg(fd, &msgh, MSG_NOSIGNAL)) < 0)
  && (errno == EINTR)) ;
- if (count < 0 || count != expected)
+ if (count < 0)
+ return -1;
+ if (count != expected) {
+ errno = EBADMSG;
  return -1;
+ }
 
  return 0;
 }
@@ -140,8 +146,10 @@ receive_response(int fd, uint32_t function, char **outdata, int32_t * ret_val)
  struct iovec resp_data;
  ssize_t count;
 
- if (fd < 0)
+ if (fd < 0) {
+ errno = EINVAL;
  return -1;
+ }
 
  resp_hdr[0].iov_base = &func;
  resp_hdr[0].iov_len = sizeof(func);
@@ -151,11 +159,17 @@ receive_response(int fd, uint32_t function, char **outdata, int32_t * ret_val)
  resp_hdr[2].iov_len = sizeof(*ret_val);
 
  while (((count = readv(fd, resp_hdr, 3)) < 0) && (errno == EINTR)) ;
+ if (count < 0) {
+ return -1;
+ }
+
  if (count != (sizeof(func) + sizeof(data_size) + sizeof(*ret_val))) {
+ errno = EBADMSG;
  return -1;
  }
 
  if (func != function || !data_size || data_size > MAX_DATA_BUF) {
+ errno = EBADMSG;
  return -1;
  }
 
@@ -172,6 +186,8 @@ receive_response(int fd, uint32_t function, char **outdata, int32_t * ret_val)
  if (count < 0 || (uint32_t) count != data_size ||
  data[data_size - 1] != '\0') {
  free(data);
+ if (count >= 0)
+ errno = EBADMSG;
  return -1;
  }
  *outdata = data;