From 2c42257314536b94cc8d52edede86e94e98c1436 Mon Sep 17 00:00:00 2001

From: Florian Weimer <fweimer@redhat.com>

Date: Fri, 14 Oct 2022 11:02:25 +0200

Subject: [PATCH] elf: Do not completely clear reused namespace in dlmopen (bug

 29600)

Content-type: text/plain; charset=UTF-8

The data in the _ns_debug member must be preserved, otherwise

_dl_debug_initialize enters an infinite loop.  To be conservative,

only clear the libc_map member for now, to fix bug 29528.

Fixes commit d0e357ff45a75553dee3b17ed7d303bfa544f6fe

("elf: Call __libc_early_init for reused namespaces (bug 29528)"),

by reverting most of it.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

Tested-by: Carlos O'Donell <carlos@redhat.com>

---

 elf/dl-open.c           | 14 ++++++--------

 elf/tst-dlmopen-twice.c | 28 ++++++++++++++++++++++++----

 2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/elf/dl-open.c b/elf/dl-open.c

index 46e8066fd8..e7db5e9642 100644

--- a/elf/dl-open.c

+++ b/elf/dl-open.c

@@ -836,15 +836,13 @@ _dl_open (const char *file, int mode, co

 	  _dl_signal_error (EINVAL, file, NULL, N_("\

 no more namespaces available for dlmopen()"));

 	}

+      else if (nsid == GL(dl_nns))

+	{

+	  __rtld_lock_initialize (GL(dl_ns)[nsid]._ns_unique_sym_table.lock);

+	  ++GL(dl_nns);

+	}

-      if (nsid == GL(dl_nns))

-	++GL(dl_nns);

-

-      /* Initialize the new namespace.  Most members are

-	 zero-initialized, only the lock needs special treatment.  */

-      memset (&GL(dl_ns)[nsid], 0, sizeof (GL(dl_ns)[nsid]));

-      __rtld_lock_initialize (GL(dl_ns)[nsid]._ns_unique_sym_table.lock);

-

+      GL(dl_ns)[nsid].libc_map = NULL;

       _dl_debug_initialize (0, nsid)->r_state = RT_CONSISTENT;

     }

   /* Never allow loading a DSO in a namespace which is empty.  Such

diff --git a/elf/tst-dlmopen-twice.c b/elf/tst-dlmopen-twice.c

index 449f3c8fa9..70c71fe19c 100644

--- a/elf/tst-dlmopen-twice.c

+++ b/elf/tst-dlmopen-twice.c

@@ -16,18 +16,38 @@

    License along with the GNU C Library; if not, see

    <https://www.gnu.org/licenses/>.  */

-#include <support/xdlfcn.h>

+#include <stdio.h>

 #include <support/check.h>

+#include <support/xdlfcn.h>

-static int

-do_test (void)

+/* Run the test multiple times, to check finding a new namespace while

+   another namespace is already in use.  This used to trigger bug 29600.  */

+static void

+recurse (int depth)

 {

-  void *handle = xdlmopen (LM_ID_NEWLM, "tst-dlmopen-twice-mod1.so", RTLD_NOW);

+  if (depth == 0)

+    return;

+

+  printf ("info: running at depth %d\n", depth);

+  void *handle = xdlmopen (LM_ID_NEWLM, "tst-dlmopen-twice-mod1.so",

+                           RTLD_NOW);

   xdlclose (handle);

   handle = xdlmopen (LM_ID_NEWLM, "tst-dlmopen-twice-mod2.so", RTLD_NOW);

   int (*run_check) (void) = xdlsym (handle, "run_check");

   TEST_COMPARE (run_check (), 0);

+  recurse (depth - 1);

   xdlclose (handle);

+}

+

+static int

+do_test (void)

+{

+  /* First run the test without nesting.  */

+  recurse (1);

+

+  /* Then with nesting.  The constant needs to be less than the

+     internal DL_NNS namespace constant.  */

+  recurse (10);

   return 0;

 }

-- 

2.31.1