From: Cliff Wickman <cpw@sgi.com>
Date: Mon, 23 Jun 2008 13:32:25 +0000 (-0500)
Subject: x86, SGI UV: uv_ptc_proc_write fix
X-Git-Tag: v2.6.27-rc1~1106^2~244^2
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=e7eb8726d0e144f0925972c4ecee945e91a42753;p=linux-2.6-omap-h63xx.git

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>
---

diff --git a/arch/x86/kernel/tlb_uv.c b/arch/x86/kernel/tlb_uv.c
index c503b7f0448..d0fbb7712ab 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;