Re: [PATCH] elf: Never use the file ID of the main executable [BZ #24900]

["Gabriel F. T. Gomes" <gabriel@inconstante.net.br>]

Hi, Florian,

On Thu, 22 Aug 2019, Florian Weimer wrote:

>If the loader is invoked explicitly and loads the main executable,
>it stores the file ID of the main executable in l_file_id.  This
>information is not available if the main excutable is loaded by the
>kernel, so this is another case where the two cases differ.
>
>This enhances commit 23d2e5faf0bca6d9b31bef4aa162b95ee64cbfc6
>("elf: Self-dlopen failure with explict loader invocation
>[BZ #24900]").

As we discussed at Cauldron, I had reviewed this patch and noticed that it
changes the place where elf/tst-dlopen-aout fails.

Before this patch, it fails in the test case itself , at:

error: tst-dlopen-aout.c:48: dlopen succeeded unexpectedly: elf/tst-dlopen-aout

After this patch, it fails at:

elf/dl-tls.c: 517: _dl_allocate_tls_init: Assertion `listp != NULL' failed!

which, as you explained to me at Cauldron, is expected and will only be
solved with a sebsequent patch [1].  As you also mentioned to me at
Cauldron, reviewing the second patch is a little tricky, but I'll try to
do it.

[1] https://sourceware.org/ml/libc-alpha/2019-08/msg00625.html

>-  /* Get file information.  */
>+  /* Get file information.  To match the kernel behavior, do not fill
>+     in this information for the executable in case of an explicit
>+     loader invocation.  */
>   struct r_file_id id;
>+  if (mode & __RTLD_OPENEXEC)
>+    {
>+      assert (nsid == LM_ID_BASE);
>+      memset (&id, 0, sizeof (id));
>+    }
>+  else
>+    {

OK.

I think that this patch does the right thing and could be committed.

Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>

Thanks!