[glibc] elf: Replace `strcpy` call with `memcpy` [BZ #29454]

[Noah Goldstein <nwg@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=483cfe1a6a33d6335b1901581b41040d2d412511

commit 483cfe1a6a33d6335b1901581b41040d2d412511
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Mon Aug 8 11:26:22 2022 +0800

    elf: Replace `strcpy` call with `memcpy` [BZ #29454]
    
    GCC normally does this optimization for us in
    strlen_pass::handle_builtin_strcpy but only for optimized
    build. To avoid needing to include strcpy.S in the rtld build to
    support the debug build, just do the optimization by hand.

Diff:
---
 elf/dl-cache.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 8bbf110d02..b97c17b3a9 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -509,8 +509,9 @@ _dl_load_cache_lookup (const char *name)
      we are accessing. Therefore we must make the copy of the
      mapping data without using malloc.  */
   char *temp;
-  temp = alloca (strlen (best) + 1);
-  strcpy (temp, best);
+  size_t best_len = strlen (best) + 1;
+  temp = alloca (best_len);
+  memcpy (temp, best, best_len);
   return __strdup (temp);
 }