From: Johannes Berg <johannes@sipsolutions.net>
To: Matthias Kaehlcke <mka@chromium.org>,
"David S . Miller" <davem@davemloft.net>,
Felix Fietkau <nbd@openwrt.org>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Grant Grundler <grundler@chromium.org>
Subject: Re: [PATCH] cfg80211: Fix array-bounds warning in fragment copy
Date: Mon, 27 Mar 2017 12:47:59 +0200 [thread overview]
Message-ID: <1490611679.3393.0.camel@sipsolutions.net> (raw)
In-Reply-To: <20170325010644.190368-1-mka@chromium.org> (sfid-20170325_020717_155658_DF54EC50)
On Fri, 2017-03-24 at 18:06 -0700, Matthias Kaehlcke wrote:
> __ieee80211_amsdu_copy_frag intentionally initializes a pointer to
> array[-1] to increment it later to valid values. clang rightfully
> generates an array-bounds warning on the initialization statement.
> Work around this by initializing the pointer to array[0] and
> decrementing it later, which allows to leave the rest of the
> algorithm untouched.
>
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> ---
> net/wireless/util.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/wireless/util.c b/net/wireless/util.c
> index 68e5f2ecee1a..d3d459e4a070 100644
> --- a/net/wireless/util.c
> +++ b/net/wireless/util.c
> @@ -659,7 +659,7 @@ __ieee80211_amsdu_copy_frag(struct sk_buff *skb,
> struct sk_buff *frame,
> int offset, int len)
> {
> struct skb_shared_info *sh = skb_shinfo(skb);
> - const skb_frag_t *frag = &sh->frags[-1];
> + const skb_frag_t *frag = &sh->frags[0];
> struct page *frag_page;
> void *frag_ptr;
> int frag_len, frag_size;
> @@ -669,6 +669,7 @@ __ieee80211_amsdu_copy_frag(struct sk_buff *skb,
> struct sk_buff *frame,
> frag_page = virt_to_head_page(skb->head);
> frag_ptr = skb->data;
> frag_size = head_size;
> + frag--;
Isn't it just a question of time until the compiler will see through
this trick and warn about it?
johannes
next prev parent reply other threads:[~2017-03-27 10:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-25 1:06 [PATCH] cfg80211: Fix array-bounds warning in fragment copy Matthias Kaehlcke
2017-03-27 10:47 ` Johannes Berg [this message]
2017-03-27 11:29 ` Felix Fietkau
2017-03-27 11:38 ` Johannes Berg
2017-03-27 19:32 ` Matthias Kaehlcke
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