linux-kernel - [PATCH 2/5] fork,random: use get_random_canary to set tsk->stack

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Message-Id: <20170524155751.424-3-riel@redhat.com>
Date:   Wed, 24 May 2017 11:57:48 -0400
From:   riel@...hat.com
To:     linux-kernel@...r.kernel.org
Cc:     danielmicay@...il.com, tytso@....edu, keescook@...omium.org,
        hpa@...or.com, luto@...capital.net, mingo@...nel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, linux-sh@...r.kernel.org,
        ysato@...rs.sourceforge.jp, kernel-hardening@...ts.openwall.com
Subject: [PATCH 2/5] fork,random: use get_random_canary to set tsk->stack_canary

From: Rik van Riel <riel@...hat.com>

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.

Signed-off-by: Rik van Riel <riel@...hat.com>
---
 kernel/fork.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index aa1076c5e4a9..b3591e9250a8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -560,7 +560,7 @@ 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
 
 	/*
-- 
2.9.3