linux-kernel - Re: [PATCH v2 2/3] test_overflow: Add shift overflow tests

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Date:   Tue, 31 Jul 2018 20:13:53 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Kees Cook <keescook@...omium.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Leon Romanovsky <leon@...nel.org>,
        Bart Van Assche <Bart.VanAssche@....com>,
        Doug Ledford <dledford@...hat.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] test_overflow: Add shift overflow tests

On Tue, Jul 31, 2018 at 05:00:38PM -0700, Kees Cook wrote:
> +	/* Overflow: high bit falls off. */
> +	/* 10010110 */
> +	err |= TEST_ONE_SHIFT(150, 1, u8, 0, true);
> +	/* 1000100010010110 */
> +	err |= TEST_ONE_SHIFT(34966, 1, u16, 0, true);
> +	/* 10000100000010001000100010010110 */
> +	err |= TEST_ONE_SHIFT(2215151766U, 1, u32, 0, true);
> +	err |= TEST_ONE_SHIFT(2215151766U, 1, unsigned int, 0, true);
> +	/* 1000001000010000010000000100000010000100000010001000100010010110 */
> +	err |= TEST_ONE_SHIFT(9372061470395238550ULL, 1, u64, 0, true);

This same idea should be repeated with signed outputs and check both
overflow past the end (<<2) and overflow into the signed bit (<<1)

        /* Overflow, high bit falls into the sign bit or off the end */
	/* 01001011 */
	err |= TEST_ONE_SHIFT(75, 1, s8, 0, true);
	err |= TEST_ONE_SHIFT(75, 2, s8, 0, true);

And also general type mismatch overflow:

	err |= TEST_ONE_SHIFT(0x100, 0, u8, 0, true);
	err |= TEST_ONE_SHIFT(0xFF, 0, s8, 0, true);

Thanks,
Jason