Don't refuse to start on systems using GNU stow, graft, STORE et al

There are multiple package management systems out there which implement
packages using symlinks. The recent (otherwise useful) check to ensure that
a re-executed pulseaudio is actually reexecuting itself unfortunately breaks
in the presence of all these packaging systems, because PA_BINARY refers
to its installed location (e.g. /usr/local/bin/pulseaudio), which is a
symlink to the binary (e.g. /usr/local/stow/pulseaudio-0.9.18/bin/pulseaudio),
because /proc/self/exe always contains the canonical path of the executable,
with all symlinks resolved.

(At least one distribution uses a symlink-based packaging system, so
will be forced to apply this locally in any case.)

The fix is simple: canonicalize PA_BINARY before equality-testing. (This
should be completely safe, because the OS does just that when PA_BINARY
is executed.)

The patch is against 0.9.18, but applies without fuzz to current master.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/daemon/main.c b/src/daemon/main.c
index af59adef..2e16c187 100644
--- a/src/daemon/main.c
+++ b/src/daemon/main.c
@@ -416,23 +416,28 @@ int main(int argc, char *argv[]) {
 
     if (!getenv("LD_BIND_NOW")) {
         char *rp;
+        char *canonical_rp;
 
         /* We have to execute ourselves, because the libc caches the
          * value of $LD_BIND_NOW on initialization. */
 
         pa_set_env("LD_BIND_NOW", "1");
 
+        canonical_rp = pa_realpath(PA_BINARY);
+
         if ((rp = pa_readlink("/proc/self/exe"))) {
 
-            if (pa_streq(rp, PA_BINARY))
+            if (pa_streq(rp, canonical_rp))
                 pa_assert_se(execv(rp, argv) == 0);
             else
-                pa_log_warn("/proc/self/exe does not point to " PA_BINARY ", cannot self execute. Are you playing games?");
+                pa_log_warn("/proc/self/exe does not point to %s, cannot self execute. Are you playing games?", canonical_rp);
 
             pa_xfree(rp);
 
         } else
             pa_log_warn("Couldn't read /proc/self/exe, cannot self execute. Running in a chroot()?");
+
+        pa_xfree(canonical_rp);
     }
 #endif