journal: guarantee async-signal-safety in sd_journald_sendv

signal(7) provides a list of functions which may be called from a
signal handler. Other functions, which only call those functions and
don't access global memory and are reentrant are also safe.
sd_j_sendv was mostly OK, but would call mkostemp and writev in a
fallback path, which are unsafe.

Being able to call sd_j_sendv in a async-signal-safe way is important
because it allows it be used in signal handlers.

Safety is achieved by replacing mkostemp with open(O_TMPFILE) and an
open-coded writev replacement which uses write. Unfortunately,
O_TMPFILE is only available on kernels >= 3.11. When O_TMPFILE is
unavailable, an open-coded mkostemp is used.

https://bugzilla.gnome.org/show_bug.cgi?id=722889

1 files changed, 1 insertions, 1 deletions

diff --git a/src/journal/journal-send.c b/src/journal/journal-send.c
index ca9199f71..960c5776b 100644
--- a/src/journal/journal-send.c
+++ b/src/journal/journal-send.c
@@ -314,7 +314,7 @@ _public_ int sd_journal_sendv(const struct iovec *iov, int n) {
         if (buffer_fd < 0)
                 return buffer_fd;
 
-        n = writev(buffer_fd, w, j);
+        n = writev_safe(buffer_fd, w, j);
         if (n < 0) {
                 close_nointr_nofail(buffer_fd);
                 return -errno;