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Date:   Wed, 9 Dec 2020 15:55:40 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Michal Kubecek <mkubecek@suse.cz>
Cc:     "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] ethtool: fix stack overflow in ethnl_parse_bitset()
Message-ID: <20201209155540.7217ee8a@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com>
In-Reply-To: <3487ee3a98e14cd526f55b6caaa959d2dcbcad9f.1607465316.git.mkubecek@suse.cz>
References: <3487ee3a98e14cd526f55b6caaa959d2dcbcad9f.1607465316.git.mkubecek@suse.cz>
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On Tue,  8 Dec 2020 23:13:51 +0100 (CET) Michal Kubecek wrote:
> Syzbot reported a stack overflow in bitmap_from_arr32() called from
> ethnl_parse_bitset() when bitset from netlink message is longer than
> target bitmap length. While ethnl_compact_sanity_checks() makes sure that
> trailing part is all zeros (i.e. the request does not try to touch bits
> kernel does not recognize), we also need to cap change_bits to nbits so
> that we don't try to write past the prepared bitmaps.
> 
> Fixes: 88db6d1e4f62 ("ethtool: add ethnl_parse_bitset() helper")
> Reported-by: syzbot+9d39fa49d4df294aab93@syzkaller.appspotmail.com
> Signed-off-by: Michal Kubecek <mkubecek@suse.cz>

Applied, thank you!