[RFC PATCH 5/7] kernel/kthread.c: do runtime check of format string in kthread_create_on_cpu()

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Kees Cook <keescook@chromium.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	"Steven Rostedt (VMware)" <rostedt@goodmis.org>
Subject: [RFC PATCH 5/7] kernel/kthread.c: do runtime check of format string in kthread_create_on_cpu()
Date: Sat, 27 Oct 2018 01:24:07 +0200	[thread overview]
Message-ID: <20181026232409.16100-6-linux@rasmusvillemoes.dk> (raw)
In-Reply-To: <20181026232409.16100-1-linux@rasmusvillemoes.dk>

One is supposed to pass in a format string containing (at most) one %u
instance. Use fmtcheck() to enforce that at runtime, WARNing and falling
back to a harmless "kthread/%u" in case verification fails.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 kernel/kthread.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 087d18d771b5..fddfe605632b 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -441,8 +441,8 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
 {
 	struct task_struct *p;
 
-	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
-				   cpu);
+	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu),
+				   fmtcheck(namefmt, "kthread/%u", 0), cpu);
 	if (IS_ERR(p))
 		return p;
 	kthread_bind(p, cpu);
-- 
2.19.1.6.gbde171bbf5

