dlfcn: Do not use rtld_active () to determine ld.so state (bug 29078)

When audit modules are loaded, ld.so initialization is not yet
complete, and rtld_active () returns false even though ld.so is
mostly working.  Instead, the static dlopen hook is used, but that
does not work at all because this is not a static dlopen situation.

Commit 466c1ea15f461edb8e3ffaf5d86d708876343bbf ("dlfcn: Rework
static dlopen hooks") moved the hook pointer into _rtld_global_ro,
which means that separate protection is not needed anymore and the
hook pointer can be checked directly.

The guard for disabling libio vtable hardening in _IO_vtable_check
should stay for now.

Fixes commit 8e1472d2c1e25e6eabc2059170731365f6d5b3d1 ("ld.so:
Examine GLRO to detect inactive loader [BZ #20204]").

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/elf/dl-libc.c b/elf/dl-libc.c
index a7180d0af8..266e068da6 100644
--- a/elf/dl-libc.c
+++ b/elf/dl-libc.c
@@ -156,7 +156,7 @@ __libc_dlopen_mode (const char *name, int mode)
   args.caller_dlopen = RETURN_ADDRESS (0);
 
 #ifdef SHARED
-  if (!rtld_active ())
+  if (GLRO (dl_dlfcn_hook) != NULL)
     return GLRO (dl_dlfcn_hook)->libc_dlopen_mode (name, mode);
 #endif
   return dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map;
@@ -184,7 +184,7 @@ __libc_dlsym (void *map, const char *name)
   args.name = name;
 
 #ifdef SHARED
-  if (!rtld_active ())
+  if (GLRO (dl_dlfcn_hook) != NULL)
     return GLRO (dl_dlfcn_hook)->libc_dlsym (map, name);
 #endif
   return (dlerror_run (do_dlsym, &args) ? NULL
@@ -198,7 +198,7 @@ void *
 __libc_dlvsym (void *map, const char *name, const char *version)
 {
 #ifdef SHARED
-  if (!rtld_active ())
+  if (GLRO (dl_dlfcn_hook) != NULL)
     return GLRO (dl_dlfcn_hook)->libc_dlvsym (map, name, version);
 #endif
 
@@ -221,7 +221,7 @@ int
 __libc_dlclose (void *map)
 {
 #ifdef SHARED
-  if (!rtld_active ())
+  if (GLRO (dl_dlfcn_hook) != NULL)
     return GLRO (dl_dlfcn_hook)->libc_dlclose (map);
 #endif
   return dlerror_run (do_dlclose, map);