linux-kernel - [PATCH] gpu: vga: fix ZERO_SIZE

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Message-Id: <1290361196-14999-1-git-send-email-segoon@openwall.com>
Date:	Sun, 21 Nov 2010 20:39:54 +0300
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	kernel-janitors@...r.kernel.org
Cc:	Dave Airlie <airlied@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tiago Vignatti <tiago.vignatti@...ia.com>,
	Mike Travis <travis@....com>, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] gpu: vga: fix ZERO_SIZE_PTR dereference

count is not checked before kmalloc() call, if it is -1 then
kmalloc() returns ZERO_SIZE_PTR. This pointer is then dereferenced.
Also one may pass too big count to generate OOM condition.
To prevent this limit 'count' maximum value.  PAGE_SIZE looks OK.

Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
---
 Compile tested only.

 drivers/gpu/vga/vgaarb.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index c380c65..09e3090 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -836,6 +836,8 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
 	int ret_val;
 	int i;
 
+	if (count > PAGE_SIZE)
+		count = PAGE_SIZE;
 
 	kbuf = kmalloc(count + 1, GFP_KERNEL);
 	if (!kbuf)
-- 
1.7.0.4

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