From: Rik van Riel <riel@redhat.com>
Date: Wed, 12 Jul 2017 21:36:20 +0000 (-0700)
Subject: fork,random: use get_random_canary() to set tsk->stack_canary
X-Git-Tag: v4.14-rc1~476^2~30
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7cd815bce828220deffd1654265f0ef891567774;p=platform%2Fkernel%2Flinux-rpi.git

fork,random: use get_random_canary() to set tsk->stack_canary

Use the ascii-armor canary to prevent unterminated C string overflows
from being able to successfully overwrite the canary, even if they
somehow obtain the canary value.

Inspired by execshield ascii-armor and Daniel Micay's linux-hardened
tree.

Link: http://lkml.kernel.org/r/20170524155751.424-3-riel@redhat.com
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/fork.c b/kernel/fork.c
index ade237a..17921b0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -554,7 +554,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	set_task_stack_end_magic(tsk);
 
 #ifdef CONFIG_CC_STACKPROTECTOR
-	tsk->stack_canary = get_random_long();
+	tsk->stack_canary = get_random_canary();
 #endif
 
 	/*