[systemd-devel] [PATCH] Circumvent autofs_v5_packet_union size bug

[Thomas Meyer]

the size of autofs_v5_packet_union is 300 bytes on x86 and 304 bytes on x86_64 kernels.
when running systemd (x86) on an x86_64 kernel this leads to a hang in automount_fd_event->loop_read
as a second fd_event is trigged for the remaining 4 bytes. but the loop_read tries to read
300 bytes again. adapt the packet size dynamically to architecture we are running on.

Signed-off-by: Thomas Meyer <thomas at m3y3r.de>
---
 src/automount.c |   23 ++++++++++++++++++++++-
 1 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/src/automount.c b/src/automount.c
index 29b807d..ec2c8f3 100644
--- a/src/automount.c
+++ b/src/automount.c
@@ -26,6 +26,7 @@
 #include <fcntl.h>
 #include <sys/epoll.h>
 #include <sys/stat.h>
+#include <sys/utsname.h>
 #include <linux/auto_fs4.h>
 #include <linux/auto_dev-ioctl.h>
 
@@ -744,11 +745,31 @@ static bool automount_check_gc(Unit *u) {
         return UNIT_VTABLE(UNIT(a->mount))->check_gc(UNIT(a->mount));
 }
 
+static size_t get_kpkt_len(void)
+{
+        size_t pkt_len = sizeof(struct autofs_v5_packet);
+        struct utsname un;
+
+        uname(&un);
+
+        if (pkt_len % 8) {
+                if (strcmp(un.machine, "alpha") == 0 ||
+                    strcmp(un.machine, "ia64") == 0 ||
+                    strcmp(un.machine, "x86_64") == 0 ||
+                    strcmp(un.machine, "ppc64") == 0)
+                        pkt_len += 4;
+
+        }
+
+        return pkt_len;
+}
+
 static void automount_fd_event(Unit *u, int fd, uint32_t events, Watch *w) {
         Automount *a = AUTOMOUNT(u);
         union autofs_v5_packet_union packet;
         ssize_t l;
         int r;
+        int packetsize = (int)get_kpkt_len();
 
         assert(a);
         assert(fd == a->pipe_fd);
@@ -758,7 +779,7 @@ static void automount_fd_event(Unit *u, int fd, uint32_t events, Watch *w) {
                 goto fail;
         }
 
-        if ((l = loop_read(a->pipe_fd, &packet, sizeof(packet), true)) != sizeof(packet)) {
+        if ((l = loop_read(a->pipe_fd, &packet, packetsize , true)) != packetsize) {
                 log_error("Invalid read from pipe: %s", l < 0 ? strerror(-l) : "short read");
                 goto fail;
         }
-- 
1.7.6.2

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