ldso_tls: Refetch dtv from memory if THREAD_DTV has changed

_dl_update_slotinfo might change THREAD_DTV () (if it needs to reallocate it),
but the caller (__tls_get_addr) doesn't refetch dtv from memory, it uses its
cached copy. This may crash (if dtv[GET_ADDR_MODULE] is off the cliff, or
might read uninitialized memory and return it.
Typically dtv[GET_ADDR_MODULE].pointer.val is NULL and so __tls_get_addr
returns NULL + offset_within_PT_TLS. The next time __tls_get_addr is called
for the same library it will return correct address as _dl_update_slotinfo
won't need to be called.

Signed-off-by: Jakub Jelinek <jakub@redhat.com>
Signed-off-by: Filippo Arcidiacono <filippo.arcidiacono@st.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/test/tls/tst-tlsmod18a.c b/test/tls/tst-tlsmod18a.c
new file mode 100644
index 000000000..9aba607ed
--- /dev/null
+++ b/test/tls/tst-tlsmod18a.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+#ifndef N
+# define N 0
+#endif
+
+static __thread int var = 4;
+
+int
+test (void)
+{
+  int *p = &var;
+  /* GCC assumes &var is never NULL, add optimization barrier.  */
+  __asm __volatile ("" : "+r" (p));
+  if (p == NULL || *p != 4)
+    {
+      printf ("fail %d %p\n", N, p);
+      return 1;
+    }
+  return 0;
+}