fix double-processing of DT_RELR relocations in ldso relocating itself

[musl] / src / env / __stack_chk_fail.c

diff --git a/src/env/__stack_chk_fail.c b/src/env/__stack_chk_fail.c
index e32596d..e535260 100644 (file)
--- a/src/env/__stack_chk_fail.c
+++ b/src/env/__stack_chk_fail.c
@@ -9,7 +9,16 @@ void __init_ssp(void *entropy)
        if (entropy) memcpy(&__stack_chk_guard, entropy, sizeof(uintptr_t));
        else __stack_chk_guard = (uintptr_t)&__stack_chk_guard * 1103515245;
 
-       __pthread_self()->CANARY = __stack_chk_guard;
+#if UINTPTR_MAX >= 0xffffffffffffffff
+       /* Sacrifice 8 bits of entropy on 64bit to prevent leaking/
+        * overwriting the canary via string-manipulation functions.
+        * The NULL byte is on the second byte so that off-by-ones can
+        * still be detected. Endianness is taken care of
+        * automatically. */
+       ((char *)&__stack_chk_guard)[1] = 0;
+#endif
+
+       __pthread_self()->canary = __stack_chk_guard;
 }
 
 void __stack_chk_fail(void)