[glibc] aarch64: Fix missing BTI protection from dependencies [BZ #26926]

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=72739c79f61989a76b7dd719f34fcfb7b8eadde9

commit 72739c79f61989a76b7dd719f34fcfb7b8eadde9
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Fri Nov 20 15:27:06 2020 +0000

    aarch64: Fix missing BTI protection from dependencies [BZ #26926]
    
    The _dl_open_check and _rtld_main_check hooks are not called on the
    dependencies of a loaded module, so BTI protection was missed on
    every module other than the main executable and directly dlopened
    libraries.
    
    The fix just iterates over dependencies to enable BTI.
    
    Fixes bug 26926.

Diff:
---
 sysdeps/aarch64/dl-bti.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/sysdeps/aarch64/dl-bti.c b/sysdeps/aarch64/dl-bti.c
index 196e462520..56c097210a 100644
--- a/sysdeps/aarch64/dl-bti.c
+++ b/sysdeps/aarch64/dl-bti.c
@@ -51,11 +51,24 @@ enable_bti (struct link_map *map, const char *program)
   return 0;
 }
 
-/* Enable BTI for L if required.  */
+/* Enable BTI for L and its dependencies.  */
 
 void
 _dl_bti_check (struct link_map *l, const char *program)
 {
-  if (GLRO(dl_aarch64_cpu_features).bti && l->l_mach.bti)
+  if (!GLRO(dl_aarch64_cpu_features).bti)
+    return;
+
+  if (l->l_mach.bti)
     enable_bti (l, program);
+
+  unsigned int i = l->l_searchlist.r_nlist;
+  while (i-- > 0)
+    {
+      struct link_map *dep = l->l_initfini[i];
+      if (dep->l_init_called)
+	continue;
+      if (dep->l_mach.bti)
+	enable_bti (dep, program);
+    }
 }