dlfcn: Failures after dlmopen should not terminate process [BZ #24772]

Commit 9e78f6f6e7134a5f299cc8de77370218f8019237 ("Implement
_dl_catch_error, _dl_signal_error in libc.so [BZ #16628]") has the
side effect that distinct namespaces, as created by dlmopen, now have
separate implementations of the rtld exception mechanism.  This means
that the call to _dl_catch_error from libdl in a secondary namespace
does not actually install an exception handler because the
thread-local variable catch_hook in the libc.so copy in the secondary
namespace is distinct from that of the base namepace.  As a result, a
dlsym/dlopen/... failure in a secondary namespace terminates the process
with a dynamic linker error because it looks to the exception handler
mechanism as if no handler has been installed.

This commit restores GLRO (dl_catch_error) and uses it to set the
handler in the base namespace.

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

1 files changed, 9 insertions, 0 deletions

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index ea3f7a69d0..b207f229c3 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -662,6 +662,12 @@ struct rtld_global_ro
   void *(*_dl_open) (const char *file, int mode, const void *caller_dlopen,
 		     Lmid_t nsid, int argc, char *argv[], char *env[]);
   void (*_dl_close) (void *map);
+  /* libdl in a secondary namespace (after dlopen) must use
+     _dl_catch_error from the main namespace, so it has to be
+     exported in some way.  */
+  int (*_dl_catch_error) (const char **objname, const char **errstring,
+			  bool *mallocedp, void (*operate) (void *),
+			  void *args);
   void *(*_dl_tls_get_addr_soft) (struct link_map *);
 #ifdef HAVE_DL_DISCOVER_OSVERSION
   int (*_dl_discover_osversion) (void);
@@ -900,6 +906,9 @@ extern int _dl_catch_error (const char **objname, const char **errstring,
 			    void *args);
 libc_hidden_proto (_dl_catch_error)
 
+/* Used for initializing GLRO (_dl_catch_error).  */
+extern __typeof__ (_dl_catch_error) _rtld_catch_error attribute_hidden;
+
 /* Call OPERATE (ARGS).  If no error occurs, set *EXCEPTION to zero.
    Otherwise, store a copy of the raised exception in *EXCEPTION,
    which has to be freed by _dl_exception_free.  As a special case, if