From 072af0c638dc8a5c7db2edc4dddbd6d44bee3bdb Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Mon, 2 Aug 2021 10:25:01 -0700
Subject: [PATCH] fortify: Fix dropped strcpy() compile-time write overflow check
Git-commit: 072af0c638dc8a5c7db2edc4dddbd6d44bee3bdb
Patch-mainline: v5.16-rc1
References: git-fixes
The implementation for intra-object overflow in str*-family functions
accidentally dropped compile-time write overflow checking in strcpy(),
leaving it entirely to run-time. Add back the intended check.
Fixes: 6a39e62abbaf ("lib: string.h: detect intra-object overflow in fortified string functions")
Cc: Daniel Axtens <dja@axtens.net>
Cc: Francis Laniel <laniel_francis@privacyrequired.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
include/linux/fortify-string.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 7e67d02764db..68bc5978d916 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -287,7 +287,10 @@ __FORTIFY_INLINE char *strcpy(char *p, const char *q)
if (p_size == (size_t)-1 && q_size == (size_t)-1)
return __underlying_strcpy(p, q);
size = strlen(q) + 1;
- /* test here to use the more stringent object size */
+ /* Compile-time check for const size overflow. */
+ if (__builtin_constant_p(size) && p_size < size)
+ __write_overflow();
+ /* Run-time check for dynamic size overflow. */
if (p_size < size)
fortify_panic(__func__);
memcpy(p, q, size);
--
2.26.2