X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fenv%2F__stack_chk_fail.c;h=e53526020f751d34542f07c6b30d94c5dc08bf72;hb=29e4319178cbc2a4e9f058a99ae8098d4b6ac055;hp=cc55460b46e74758f4113a9d77ce6a132d1cdd3d;hpb=19a1fe670acb3ab9ead0fe31859ca7d4fe40dd54;p=musl

diff --git a/src/env/__stack_chk_fail.c b/src/env/__stack_chk_fail.c
index cc55460b..e5352602 100644
--- a/src/env/__stack_chk_fail.c
+++ b/src/env/__stack_chk_fail.c
@@ -9,6 +9,15 @@ 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;
 
+#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;
 }
 
@@ -16,3 +25,7 @@ void __stack_chk_fail(void)
 {
 	a_crash();
 }
+
+hidden void __stack_chk_fail_local(void);
+
+weak_alias(__stack_chk_fail, __stack_chk_fail_local);