[PATCH] elf: do not substitute dst in $LD_LIBRARY_PATH twice [BZ #22627]

[PATCH] elf: do not substitute dst in $LD_LIBRARY_PATH twice [BZ #22627]

[Dmitry V. Levin]

Starting with commit
glibc-2.18.90-470-g2a939a7e6d81f109d49306bc2e10b4ac9ceed8f9 that
introduced substitution of dynamic string tokens in fillin_rpath,
_dl_init_paths invokes _dl_dst_substitute for $LD_LIBRARY_PATH twice:
the first time it's called directly, the second time the result
is passed on to fillin_rpath which calls expand_dynamic_string_token
which in turn calls _dl_dst_substitute, leading to the following
behaviour:

$ mkdir -p /tmp/'$ORIGIN' && cd /tmp/'$ORIGIN' &&
  echo 'int main(){}' |gcc -xc - &&
  strace -qq -E LD_LIBRARY_PATH='$ORIGIN' -e /open ./a.out
open("/tmp//tmp/$ORIGIN/tls/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/tmp//tmp/$ORIGIN/tls/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/tmp//tmp/$ORIGIN/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/tmp//tmp/$ORIGIN/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3

Fix this by removing the direct _dl_dst_substitute invocation.

* elf/dl-load.c (_dl_init_paths): Remove _dl_dst_substitute preparatory
code and invocation.
---
 elf/dl-load.c | 20 +-------------------
 1 file changed, 1 insertion(+), 19 deletions(-)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index bbd3be9e..e7d97dc 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -773,41 +773,23 @@ _dl_init_paths (const char *llp)
 
   if (llp != NULL && *llp != '\0')
     {
-      char *llp_tmp;
-
-#ifdef SHARED
-      /* Expand DSTs.  */
-      size_t cnt = DL_DST_COUNT (llp, 1);
-      if (__glibc_likely (cnt == 0))
-	llp_tmp = strdupa (llp);
-      else
-	{
-	  /* Determine the length of the substituted string.  */
-	  size_t total = DL_DST_REQUIRED (l, llp, strlen (llp), cnt);
-
-	  /* Allocate the necessary memory.  */
-	  llp_tmp = (char *) alloca (total + 1);
-	  llp_tmp = _dl_dst_substitute (l, llp, llp_tmp, 1);
-	}
-#else
-      llp_tmp = strdupa (llp);
-#endif
+      char *llp_tmp = strdupa (llp);
 
       /* Decompose the LD_LIBRARY_PATH contents.  First determine how many
 	 elements it has.  */
       size_t nllp = 1;
       for (const char *cp = llp_tmp; *cp != '\0'; ++cp)
 	if (*cp == ':' || *cp == ';')
 	  ++nllp;
 
       env_path_list.dirs = (struct r_search_path_elem **)
 	malloc ((nllp + 1) * sizeof (struct r_search_path_elem *));
       if (env_path_list.dirs == NULL)
 	{
 	  errstring = N_("cannot create cache for search path");
 	  goto signal_error;
 	}
 
       (void) fillin_rpath (llp_tmp, env_path_list.dirs, ":;",
 			   __libc_enable_secure, "LD_LIBRARY_PATH",
 			   NULL, l);
-- 
ldv

Re: [PATCH] elf: do not substitute dst in $LD_LIBRARY_PATH twice [BZ #22627]

[Andreas Schwab]

On Dez 18 2017, "Dmitry V. Levin" <ldv@altlinux.org> wrote:

> * elf/dl-load.c (_dl_init_paths): Remove _dl_dst_substitute preparatory
> code and invocation.

Ok.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Re: [PATCH] elf: do not substitute dst in $LD_LIBRARY_PATH twice [BZ #22627]

[Andreas Schwab]

Please reference the bug in the changelog entry.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Re: [PATCH] elf: do not substitute dst in $LD_LIBRARY_PATH twice [BZ #22627]

[Joseph Myers]

I sort of think this shows we need better test coverage for these 
substitutions (presumably involving a test creating a $ORIGIN directory, 
in this case).

-- 
Joseph S. Myers
joseph@codesourcery.com