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Date: Fri, 28 Apr 2017 18:18:40 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
David.Laight@...lab.com, kernel-hardening@...ts.openwall.com,
davem@...emloft.net
Subject: Re: [PATCH v6 1/5] skbuff: return -EMSGSIZE in skb_to_sgvec to
prevent overflow
2017-04-25, 20:47:30 +0200, Jason A. Donenfeld wrote:
> This is a defense-in-depth measure in response to bugs like
> 4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec"). While
> we're at it, we also limit the amount of recursion this function is
> allowed to do. Not actually providing a bounded base case is a future
> diaster that we can easily avoid here.
>
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
> Changes v5->v6:
> * Use unlikely() for the rare overflow conditions.
> * Also bound recursion, since this is a potential disaster we can avert.
>
> net/core/skbuff.c | 31 ++++++++++++++++++++++++-------
> 1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index f86bf69cfb8d..24fb53f8534e 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3489,16 +3489,22 @@ void __init skb_init(void)
> * @len: Length of buffer space to be mapped
> *
> * Fill the specified scatter-gather list with mappings/pointers into a
> - * region of the buffer space attached to a socket buffer.
> + * region of the buffer space attached to a socket buffer. Returns either
> + * the number of scatterlist items used, or -EMSGSIZE if the contents
> + * could not fit.
> */
One small thing here: since you're touching this comment, could you
move it next to skb_to_sgvec, since that's the function it's supposed
to document?
Thanks!
> static int
> -__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
> +__skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len,
> + unsigned int recursion_level)
--
Sabrina
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