[PATCH 1/1] dl-load: add memory barrier before updating the next.

[Maninder Singh <maninder1 dot s at samsung dot com>]

This patch adds memory barrier before updating the liblist next.

Issue Fix: race condition between add_name_to_object  & _dl_name_match_p.
One threads calling dlopen which further calls add_name_to_object &
other thread trying to resolve RTLD_LAZY symbols through _dl_runtime_resolve
which further calls.

_dl_name_match_p checks if libname->next is valid, then it assumes
libname->next->name to be valid. Also add_name_to_object initialized name
first and then sets valid next pointer.

This patch avoids any reorder of instruction when next is set before name
to avoid any race.

Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Signed-off-by: Vaneet Narang <v.narang@samsung.com>
---
 elf/dl-load.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 016a99c..c1e69b8 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -429,6 +429,7 @@ add_name_to_object (struct link_map *l, const char *name)
   newname->name = memcpy (newname + 1, name, name_len);
   newname->next = NULL;
   newname->dont_free = 0;
+  atomic_write_barrier ();
   lastp->next = newname;
 }
 
-- 
1.9.1