linux-kernel - Re: [RFC][PATCH 3/3] audit: Audit proc cmdline value

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Message-ID: <20140106170855.GA1828@mguzik.redhat.com>
Date:	Mon, 6 Jan 2014 18:08:56 +0100
From:	Mateusz Guzik <mguzik@...hat.com>
To:	William Roberts <bill.c.roberts@...il.com>
Cc:	linux-audit@...hat.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, rgb@...hat.com,
	viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
	sds@...ho.nsa.gov, William Roberts <wroberts@...sys.com>
Subject: Re: [RFC][PATCH 3/3] audit: Audit proc cmdline value

I can't comment on the concept, but have one nit.

On Mon, Jan 06, 2014 at 07:30:30AM -0800, William Roberts wrote:
> +static void audit_log_cmdline(struct audit_buffer *ab, struct task_struct *tsk,
> +			 struct audit_context *context)
> +{
> +	int res;
> +	char *buf;
> +	char *msg = "(null)";
> +	audit_log_format(ab, " cmdline=");
> +
> +	/* Not  cached */
> +	if (!context->cmdline) {
> +		buf = kmalloc(PATH_MAX, GFP_KERNEL);
> +		if (!buf)
> +			goto out;
> +		res = get_cmdline(tsk, buf, PATH_MAX);
> +		/* Ensure NULL terminated */
> +		if (buf[res-1] != '\0')
> +			buf[res-1] = '\0';

This accesses memory below the buffer if get_cmdline returned 0, which I
believe will be the case when someone jokingly unmaps the area (all
maybe when it is swapped out but can't be swapped in due to I/O errors).

Also since you are just putting 0 in there anyway I don't see much point
in testing for it.

> +		context->cmdline = buf;
> +	}
> +	msg = context->cmdline;
> +out:
> +	audit_log_untrustedstring(ab, msg);
> +}
> +



-- 
Mateusz Guzik
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