From e7eb8726d0e144f0925972c4ecee945e91a42753 Mon Sep 17 00:00:00 2001
From: Cliff Wickman <cpw@sgi.com>
Date: Mon, 23 Jun 2008 08:32:25 -0500
Subject: [PATCH] x86, SGI UV: uv_ptc_proc_write fix

Someone could write 0 bytes to /proc/sgi_uv/ptc_statistics,
causing
  optstr[count - 1] = '\0';
to write to who-knows-where.

(Andi Kleen noticed this need from a patch I sent for
 similar code in the ia64 world (sn2_ptc_proc_write()).)

(count less than zero is not possible here, as count is unsigned)

Signed-off-by: Cliff Wickman <cpw@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/tlb_uv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/tlb_uv.c b/arch/x86/kernel/tlb_uv.c
index c503b7f04481a..d0fbb7712ab05 100644
--- a/arch/x86/kernel/tlb_uv.c
+++ b/arch/x86/kernel/tlb_uv.c
@@ -492,7 +492,7 @@ static ssize_t uv_ptc_proc_write(struct file *file, const char __user *user,
 	long newmode;
 	char optstr[64];
 
-	if (count > 64)
+	if (count == 0 || count > sizeof(optstr))
 		return -EINVAL;
 	if (copy_from_user(optstr, user, count))
 		return -EFAULT;