linux-kernel - Re: [PATCH] thunderbolt: property: fix a buffer overflow and a missing check

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Message-ID: <20190325100104.GE3622@lahna.fi.intel.com>
Date:   Mon, 25 Mar 2019 12:01:04 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Kangjie Lu <kjlu@....edu>
Cc:     pakki001@....edu, Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thunderbolt: property: fix a buffer overflow and a
 missing check

On Sun, Mar 24, 2019 at 05:49:16PM -0500, Kangjie Lu wrote:
> First, no memory is allocated for "property->value.text"; the
> following strcpy will lead to a buffer overflow.

It is actually member of union so assigning via value.txt or value.data
is the same.

So no buffer overflow.

> Second, no check is enforced for the return value of kzalloc,
> which may lead to NULL-pointer dereference.

Yes, this is valid.

Can you fix the changelog accordingly and resend?

> 
> The patch fixes the two issues.
> 
> Signed-off-by: Kangjie Lu <kjlu@....edu>
> ---
>  drivers/thunderbolt/property.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thunderbolt/property.c b/drivers/thunderbolt/property.c
> index 841314deb446..d5b0cdb8f0b1 100644
> --- a/drivers/thunderbolt/property.c
> +++ b/drivers/thunderbolt/property.c
> @@ -587,7 +587,12 @@ int tb_property_add_text(struct tb_property_dir *parent, const char *key,
>  		return -ENOMEM;
>  
>  	property->length = size / 4;
> -	property->value.data = kzalloc(size, GFP_KERNEL);
> +	property->value.text = kzalloc(size, GFP_KERNEL);
> +	if (!property->value.text) {
> +		kfree(property);
> +		return -ENOMEM;
> +	}
> +
>  	strcpy(property->value.text, text);
>  
>  	list_add_tail(&property->list, &parent->properties);
> -- 
> 2.17.1