dlsym: Make RTLD_NEXT prefer default version definition [BZ #14932]

When the first object providing foo defines both foo@v1 and foo@@v2,
dlsym(RTLD_NEXT, "foo") returns foo@v1 while dlsym(RTLD_DEFAULT, "foo")
returns foo@@v2.  The issue is that RTLD_DEFAULT uses the
DL_LOOKUP_RETURN_NEWEST flag while RTLD_NEXT doesn't.  Fix the RTLD_NEXT
branch to use DL_LOOKUP_RETURN_NEWEST.

Note: the new behavior matches FreeBSD rtld.  Future sanitizers will not
need to add versioned interceptors like https://reviews.llvm.org/D96348

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

5 files changed, 77 insertions, 1 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 838fe39afb..bfc9179fc5 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -426,6 +426,7 @@ tests += \
   tst-initorder2 \
   tst-latepthread \
   tst-main1 \
+  tst-next-ver \
   tst-nodelete2 \
   tst-nodelete-dlclose \
   tst-nodelete-opened \
@@ -712,6 +713,7 @@ modules-names += \
   neededobj6 \
   nextmod1 \
   nextmod2 \
+  nextmod3 \
   nodel2mod1 \
   nodel2mod2 \
   nodel2mod3 \
@@ -1690,6 +1692,9 @@ $(objpfx)reldep4.out: $(objpfx)reldep4mod1.so $(objpfx)reldep4mod2.so
 $(objpfx)next: $(objpfx)nextmod1.so $(objpfx)nextmod2.so
 LDFLAGS-next = -Wl,--no-as-needed
 
+$(objpfx)tst-next-ver: $(objpfx)nextmod3.so
+LDFLAGS-tst-next-ver = -Wl,--no-as-needed
+
 $(objpfx)unload2.out: $(objpfx)unload2mod.so $(objpfx)unload2dep.so
 
 $(objpfx)lateglobal.out: $(objpfx)ltglobmod1.so $(objpfx)ltglobmod2.so
@@ -2437,6 +2442,8 @@ $(objpfx)tst-linkall-static: \
 endif
 endif
 
+LDFLAGS-nextmod3.so = -Wl,--version-script=nextmod3.map
+
 # The application depends on the DSO, and the DSO loads the plugin.
 # The plugin also depends on the DSO. This creates the circular
 # dependency via dlopen that we're testing to make sure works.
diff --git a/elf/dl-sym.c b/elf/dl-sym.c
index aa993942df..b1cf42f36d 100644
--- a/elf/dl-sym.c
+++ b/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
     {
diff --git a/elf/nextmod3.c b/elf/nextmod3.c
new file mode 100644
index 0000000000..cd7bdb36af
--- /dev/null
+++ b/elf/nextmod3.c
@@ -0,0 +1,20 @@
+int
+foo_v1 (int a)
+{
+  return 1;
+}
+asm (".symver foo_v1, foo@v1");
+
+int
+foo_v2 (int a)
+{
+  return 2;
+}
+asm (".symver foo_v2, foo@v2");
+
+int
+foo (int a)
+{
+  return 3;
+}
+asm (".symver foo, foo@@@v3");
diff --git a/elf/nextmod3.map b/elf/nextmod3.map
new file mode 100644
index 0000000000..eb0e7d7800
--- /dev/null
+++ b/elf/nextmod3.map
@@ -0,0 +1,3 @@
+v1 { };
+v2 { } v1;
+v3 { foo; } v2;
diff --git a/elf/tst-next-ver.c b/elf/tst-next-ver.c
new file mode 100644
index 0000000000..7241f9038b
--- /dev/null
+++ b/elf/tst-next-ver.c
@@ -0,0 +1,46 @@
+/* Test RTLD_DEFAULT/RTLD_NEXT when the definition has multiple versions.
+   Copyright (C) 2018-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <stdio.h>
+
+#include "testobj.h"
+
+static int
+do_test (void)
+{
+  /* Resolve to foo@@v3 in nextmod3.so, instead of
+     foo@v1 or foo@v2.  */
+  int (*fp) (int) = dlsym (RTLD_DEFAULT, "foo");
+  int res = fp (0);
+  printf ("preload (0) = %d, %s\n", res, res == 3 ? "ok" : "wrong");
+  if (res != 3)
+    return 1;
+
+  /* Resolve to foo@@v3 in nextmod3.so, instead of
+     foo@v1 or foo@v2.  */
+  fp = dlsym (RTLD_NEXT, "foo");
+  res = fp (0);
+  printf ("preload (0) = %d, %s\n", res, res == 3 ? "ok" : "wrong");
+  if (res != 3)
+    return 1;
+
+  return 0;
+}
+
+#include <support/test-driver.c>