linux-kernel - [PATCH] SGI UV: uv_ptc_proc

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Message-Id: <E1KAm9h-0002Fe-8a@eag09.americas.sgi.com>
Date:	Mon, 23 Jun 2008 08:32:25 -0500
From:	Cliff Wickman <cpw@....com>
To:	mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] SGI UV: uv_ptc_proc_write security hole



From: Cliff Wickman <cpw@....com>

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)

Diffed against 2.6.26-rc6

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

Index: linux/arch/x86/kernel/tlb_uv.c
===================================================================
--- linux.orig/arch/x86/kernel/tlb_uv.c
+++ linux/arch/x86/kernel/tlb_uv.c
@@ -492,7 +492,7 @@ static ssize_t uv_ptc_proc_write(struct 
 	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;
--
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