Re: should GNU install call matchpathcon by default?

[Jim Meyering]

Stephen Smalley <address@hidden> wrote:
...
> This issue came up recently again, see:
> https://bugzilla.redhat.com/show_bug.cgi?id=447410
>
> It appears that the patch that was merged into coreutils ends up calling
> matchpathcon_init_prefix() for each file being installed rather than
> once upon startup, and without calling matchpathcon_fini() to free the
> memory allocated by each matchpathcon_init_prefix() call.
>
> That makes it slower than necessary and leaks memory.
>
> See the bug report for the discussion.
>
> Can we get this corrected in the upstream coreutils?  Thanks.

Thanks for letting me know.  The patch below should do the job.
I didn't bother calling matchpathcon_fini, since its 6MB buffer
is still reachable.

For now, I'm leaving that code ifdef'd out, because the performance
penalty is still too high even on rawhide, when performing a few hundred
to a thousand separate install commands (about a 20x hit, when
installing to /usr).  For reference, I did this:

  # matchpathcon code all ifdef'd out:
  $ touch k; time ( for i in $(seq 200); do; install k /usr/tmp/k ;done )
   0.08s user 0.30s system 97% cpu 0.391 total
  # matchpathcon code in use:
  $ touch k; time ( for i in $(seq 200); do; ./ginstall k /usr/tmp/k ;done )
   7.19s user 1.62s system 99% cpu 8.840 total

>From a089634c855312a28f2ff3c2e7c08df5d030e2f5 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 20 May 2008 17:58:42 +0200
Subject: [PATCH] install: avoid a leak in currently-ifdef'd-out code

* src/install.c (setdefaultfilecon)
[ENABLE_WHEN_MATCHPATHCON_IS_MORE_EFFICIENT]:
Call matchpathcon_init_prefix only once.
Suggestion from Stephen Smalley.  Reported by Ben Webb in
<http://bugzilla.redhat.com/447410>.
---
 src/install.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/install.c b/src/install.c
index 964ab36..b531f45 100644
--- a/src/install.c
+++ b/src/install.c
@@ -208,6 +208,8 @@ setdefaultfilecon (char const *file)
 {
   struct stat st;
   security_context_t scontext = NULL;
+  static bool first_call = true;
+
   if (selinux_enabled != 1)
     {
       /* Indicate no context found. */
@@ -216,7 +218,7 @@ setdefaultfilecon (char const *file)
   if (lstat (file, &st) != 0)
     return;

-  if (IS_ABSOLUTE_FILE_NAME (file))
+  if (first_call && IS_ABSOLUTE_FILE_NAME (file))
     {
       /* Calling matchpathcon_init_prefix (NULL, "/first_component/")
         is an optimization to minimize the expense of the following
@@ -247,6 +249,7 @@ setdefaultfilecon (char const *file)
            }
        }
     }
+  first_call = false;

   /* If there's an error determining the context, or it has none,
      return to allow default context */
--
1.5.5.1.249.g68ef3