From b2eac2dedd62224df07148a9e42eae0197902c00 Mon Sep 17 00:00:00 2001
From: Laurent Bercot <ska-skaware@skarnet.org>
Date: Sun, 23 Apr 2017 00:00:10 +0000
Subject:  Align ancillary buffers on struct cmsghdr and int boundaries

---
 src/libunixonacid/unixmessage_receive.c      | 10 ++++++++--
 src/libunixonacid/unixmessage_sender_flush.c | 13 ++++++++++---
 src/sysdeps/output-types.c                   |  2 ++
 src/sysdeps/tryancilautoclose.c              | 14 ++++++++++----
 4 files changed, 30 insertions(+), 9 deletions(-)

(limited to 'src')

diff --git a/src/libunixonacid/unixmessage_receive.c b/src/libunixonacid/unixmessage_receive.c
index 9672b63..8ca8c0b 100644
--- a/src/libunixonacid/unixmessage_receive.c
+++ b/src/libunixonacid/unixmessage_receive.c
@@ -14,6 +14,12 @@
 #include <skalibs/stralloc.h>
 #include <skalibs/unixmessage.h>
 
+union aligner_u
+{
+  struct cmsghdr cmsghdr ;
+  int i ;
+} ;
+
 static int const awesomeflags =
 #ifdef SKALIBS_HASMSGDONTWAIT
   MSG_DONTWAIT
@@ -36,7 +42,7 @@ static int const awesomeflags =
 
 static int unixmessage_receiver_fill (unixmessage_receiver_t *b)
 {
-  char ancilbuf[CMSG_SPACE(b->auxb.a - 1)] ;
+  union aligner_u ancilbuf[1 + CMSG_SPACE(b->auxb.a - 1) / sizeof(union aligner_u)] ;
   struct iovec iov[2] ;
   struct msghdr msghdr =
   {
@@ -46,7 +52,7 @@ static int unixmessage_receiver_fill (unixmessage_receiver_t *b)
     .msg_iovlen = 2,
     .msg_flags = 0,
     .msg_control = b->fds_ok & 1 ? ancilbuf : 0,
-    .msg_controllen = b->fds_ok & 1 ? sizeof(ancilbuf) : 0
+    .msg_controllen = b->fds_ok & 1 ? CMSG_SPACE(b->auxb.a - 1) : 0
   } ;
   ssize_t r = -1 ;
   if (cbuffer_isfull(&b->mainb) || ((b->fds_ok & 1) && cbuffer_isfull(&b->auxb)))
diff --git a/src/libunixonacid/unixmessage_sender_flush.c b/src/libunixonacid/unixmessage_sender_flush.c
index e7d4299..eb2645c 100644
--- a/src/libunixonacid/unixmessage_sender_flush.c
+++ b/src/libunixonacid/unixmessage_sender_flush.c
@@ -21,6 +21,13 @@
 #define MSG_NOSIGNAL 0
 #endif
 
+union aligner_u
+{
+  struct cmsghdr cmsghdr ;
+  int i ;
+} ;
+
+
  /*
     XXX: sendmsg/recvmsg is badly, badly specified.
     XXX: We assume ancillary data is attached to the first byte.
@@ -68,7 +75,7 @@ int unixmessage_sender_flush (unixmessage_sender_t *b)
       { .iov_base = pack, .iov_len = 6 },
       { .iov_base = b->data.s + offsets[b->head].left, .iov_len = len }
     } ;
-    char ancilbuf[CMSG_SPACE(nfds * sizeof(int))] ;
+    union aligner_u ancilbuf[1 + CMSG_SPACE(nfds * sizeof(int)) / sizeof(union aligner_u)] ;
     struct msghdr hdr =
     {
       .msg_name = 0,
@@ -76,7 +83,7 @@ int unixmessage_sender_flush (unixmessage_sender_t *b)
       .msg_iov = v,
       .msg_iovlen = 2,
       .msg_control = nfds ? ancilbuf : 0,
-      .msg_controllen = nfds ? sizeof(ancilbuf) : 0
+      .msg_controllen = nfds ? CMSG_SPACE(nfds * sizeof(int)) : 0
     } ;
     uint32_pack_big(pack, (uint32_t)len) ;
     uint16_pack_big(pack + 4, (uint16_t)nfds) ;
@@ -84,7 +91,7 @@ int unixmessage_sender_flush (unixmessage_sender_t *b)
     {
       struct cmsghdr *cp = CMSG_FIRSTHDR(&hdr) ;
       size_t i = 0 ;
-      memset(ancilbuf, 0, sizeof(ancilbuf)) ;
+      memset(hdr.msg_control, 0, hdr.msg_controllen) ;
       cp->cmsg_level = SOL_SOCKET ;
       cp->cmsg_type = SCM_RIGHTS ;
       cp->cmsg_len = CMSG_LEN(nfds * sizeof(int)) ;
diff --git a/src/sysdeps/output-types.c b/src/sysdeps/output-types.c
index 09995d2..22e6093 100644
--- a/src/sysdeps/output-types.c
+++ b/src/sysdeps/output-types.c
@@ -1,3 +1,5 @@
+/* ISC license. */
+
 #include <sys/types.h>
 #include <stdio.h>
 
diff --git a/src/sysdeps/tryancilautoclose.c b/src/sysdeps/tryancilautoclose.c
index c7f461f..1da87bc 100644
--- a/src/sysdeps/tryancilautoclose.c
+++ b/src/sysdeps/tryancilautoclose.c
@@ -17,9 +17,15 @@
 #include <sys/socket.h>
 #include <sys/uio.h>
 
+union aligner_u
+{
+  struct cmsghdr cmsghdr ;
+  int i ;
+} ;
+
 static int ancil_send_fd (int sock, int fd)
 {
-  char ancilbuf[CMSG_SPACE(sizeof(int))] ;
+  union aligner_u ancilbuf[1 + CMSG_SPACE(sizeof(int)) / sizeof(union aligner_u)] ;
   char s[8] = "blahblah" ;
   struct iovec v = { .iov_base = s, .iov_len = 8 } ;
   struct msghdr msghdr =
@@ -30,7 +36,7 @@ static int ancil_send_fd (int sock, int fd)
     .msg_iovlen = 1,
     .msg_flags = 0,
     .msg_control = ancilbuf,
-    .msg_controllen = sizeof(ancilbuf)
+    .msg_controllen = CMSG_SPACE(sizeof(int))
   } ;
   struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr) ;
   cmsg->cmsg_len = CMSG_LEN(sizeof(int)) ;
@@ -43,7 +49,7 @@ static int ancil_send_fd (int sock, int fd)
 
 static int ancil_recv_fd (int sock)
 {
-  char ancilbuf[CMSG_SPACE(sizeof(int))] ;
+  union aligner_u ancilbuf[1 + CMSG_SPACE(sizeof(int)) / sizeof(union aligner_u)] ;
   char s[8] ;
   struct iovec v = { .iov_base = s, .iov_len = 8 } ;
   struct msghdr msghdr =
@@ -54,7 +60,7 @@ static int ancil_recv_fd (int sock)
     .msg_iovlen = 1,
     .msg_flags = 0,
     .msg_control = ancilbuf,
-    .msg_controllen = sizeof(ancilbuf)
+    .msg_controllen = CMSG_SPACE(sizeof(int))
   } ;
   struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr) ;
   cmsg->cmsg_len = msghdr.msg_controllen ;
-- 
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