[Bug dynamic-link/14932] dlsym(handle, "foo") and dlsym(RTLD_NEXT, "foo") return different result with versioned "foo"

["i at maskray dot me" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=14932

--- Comment #7 from Fangrui Song <i at maskray dot me> ---
The issue is that dlsym(RTLD_DEFAULT, ...) sets flags to
DL_LOOKUP_RETURN_NEWEST (along with one or two other bits) while
dlsym(RTLD_NEXT, ...) passes flags==0 to dl_lookup_symbol_x.
When DL_LOOKUP_RETURN_NEWEST is in action, the default version definition is
preferred over a non-default version definition.

The following patch will make dlsym(RTLD_NEXT, ...) use DL_LOOKUP_RETURN_NEWEST
and therefore fix the bug:

--- i/elf/dl-sym.c
+++ w/elf/dl-sym.c
@@ -144,7 +144,7 @@ RTLD_NEXT used in code not dynamically loaded"));
        l = l->l_loader;

       result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope,
-                                        vers, 0, 0, match);
+                                        vers, 0, flags, match);
     }
   else
     {

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