[PATCH] gpu: vga: fix ZERO_SIZE_PTR dereference

[Vasiliy Kulikov]

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@xxxxxxxxxxxx>
---
 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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