From fc2fffe7706ef269005bf4eef56570346c9ca3da Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 5 May 2016 22:24:36 +0200
Subject: tree-wide: introduce new SOCKADDR_UN_LEN() macro, and use it
 everywhere

The macro determines the right length of a AF_UNIX "struct sockaddr_un" to pass to
connect() or bind(). It automatically figures out if the socket refers to an
abstract namespace socket, or a socket in the file system, and properly handles
the full length of the path field.

This macro is not only safer, but also simpler to use, than the usual
offsetof() + strlen() logic.
---
 src/basic/log.c         |  6 +++---
 src/basic/socket-util.h | 11 +++++++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

(limited to 'src/basic')

diff --git a/src/basic/log.c b/src/basic/log.c
index d89e6f7274..3ea643b6e6 100644
--- a/src/basic/log.c
+++ b/src/basic/log.c
@@ -165,7 +165,7 @@ static int log_open_syslog(void) {
                 goto fail;
         }
 
-        if (connect(syslog_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+        if (connect(syslog_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                 safe_close(syslog_fd);
 
                 /* Some legacy syslog systems still use stream
@@ -177,7 +177,7 @@ static int log_open_syslog(void) {
                         goto fail;
                 }
 
-                if (connect(syslog_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+                if (connect(syslog_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                         r = -errno;
                         goto fail;
                 }
@@ -215,7 +215,7 @@ static int log_open_journal(void) {
                 goto fail;
         }
 
-        if (connect(journal_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
+        if (connect(journal_fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0) {
                 r = -errno;
                 goto fail;
         }
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index d17a2f35f8..daa4b24a37 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -137,3 +137,14 @@ ssize_t next_datagram_size_fd(int fd);
 
 #define CMSG_FOREACH(cmsg, mh)                                          \
         for ((cmsg) = CMSG_FIRSTHDR(mh); (cmsg); (cmsg) = CMSG_NXTHDR((mh), (cmsg)))
+
+/* Covers only file system and abstract AF_UNIX socket addresses, but not unnamed socket addresses. */
+#define SOCKADDR_UN_LEN(sa)                                             \
+        ({                                                              \
+                const struct sockaddr_un *_sa = &(sa);                  \
+                assert(_sa->sun_family == AF_UNIX);                     \
+                offsetof(struct sockaddr_un, sun_path) +                \
+                        (_sa->sun_path[0] == 0 ?                        \
+                         1 + strnlen(_sa->sun_path+1, sizeof(_sa->sun_path)-1) : \
+                         strnlen(_sa->sun_path, sizeof(_sa->sun_path))); \
+        })
-- 
cgit v1.2.3-54-g00ecf