linux-kernel - [PATCH] x86-64: fix stack bounds checking in get

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Message-id: <20131205134017.17161.147.stgit@buzz>
Date:	Thu, 05 Dec 2013 17:40:17 +0400
From:	Konstantin Khlebnikov <k.khlebnikov@...sung.com>
To:	Andi Kleen <ak@...ux.intel.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86-64: fix stack bounds checking in get_wchan

This patch fixes potential oops on unwinding volatile stack. get_wchan() is
lockless, task may wake up at any time and override any frame under us.
Stackframe is 16 bytes long plus it's supposed to be 64bit aligned.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
---
 arch/x86/kernel/process_64.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 9c0280f..a7f089d 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -442,12 +442,11 @@ unsigned long get_wchan(struct task_struct *p)
 	if (!p || p == current || p->state == TASK_RUNNING)
 		return 0;
 	stack = (unsigned long)task_stack_page(p);
-	if (p->thread.sp < stack || p->thread.sp >= stack+THREAD_SIZE)
+	if (p->thread.sp < stack || p->thread.sp > stack + THREAD_SIZE - 8)
 		return 0;
 	fp = *(u64 *)(p->thread.sp);
 	do {
-		if (fp < (unsigned long)stack ||
-		    fp >= (unsigned long)stack+THREAD_SIZE)
+		if (fp < stack || fp > stack + THREAD_SIZE - 16 || fp & 7)
 			return 0;
 		ip = *(u64 *)(fp+8);
 		if (!in_sched_functions(ip))

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