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, 0 deletions

diff --git a/src/shared/def.h b/src/shared/def.h
index a2304fddda..7777756aad 100644
--- a/src/shared/def.h
+++ b/src/shared/def.h
@@ -44,6 +44,7 @@
 #define LOWERCASE_LETTERS "abcdefghijklmnopqrstuvwxyz"
 #define UPPERCASE_LETTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 #define LETTERS LOWERCASE_LETTERS UPPERCASE_LETTERS
+#define ALPHANUMERICAL LETTERS DIGITS
 
 #define REBOOT_PARAM_FILE "/run/systemd/reboot-param"