[PATCH v2] malloc: Fix clobbered errno when getrandom failed [BZ #29624]

[Yu Chien Peter Lin <peterlin@andestech.com>]

Save and restore errno when getrandom failed. On failure it will result
in errno clobbered at statically linked program startup. This scenario
is possible if getrandom is called by tcache_key_initialize when crng is
not ready thus EAGAIN is returned.

Fixes bug 29624.

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
---
 malloc/malloc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 953183e956..823d454c99 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3133,9 +3133,11 @@ static uintptr_t tcache_key;
 static void
 tcache_key_initialize (void)
 {
+  int saved_errno = errno;
   if (__getrandom_nocancel (&tcache_key, sizeof(tcache_key), GRND_NONBLOCK)
       != sizeof (tcache_key))
     {
+      __set_errno(saved_errno);
       tcache_key = random_bits ();
 #if __WORDSIZE == 64
       tcache_key = (tcache_key << 32) | random_bits ();
-- 
2.34.1