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Message-ID: <ZHXf29es/yh3r6jq@corigine.com> Date: Tue, 30 May 2023 13:36:59 +0200 From: Simon Horman <simon.horman@...igine.com> To: Hangyu Hua <hbh25y@...il.com> Cc: jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, simon.horman@...ronome.com, pieter.jansen-van-vuuren@....com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] net: sched: fix possible OOB write in fl_set_geneve_opt() [Updated Pieter's email address, dropped old email address of mine] On Mon, May 29, 2023 at 12:36:15PM +0800, Hangyu Hua wrote: > If we send two TCA_FLOWER_KEY_ENC_OPTS_GENEVE packets and their total > size is 252 bytes(key->enc_opts.len = 252) then > key->enc_opts.len = opt->length = data_len / 4 = 0 when the third > TCA_FLOWER_KEY_ENC_OPTS_GENEVE packet enters fl_set_geneve_opt. This > bypasses the next bounds check and results in an out-of-bounds. > > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options") > Signed-off-by: Hangyu Hua <hbh25y@...il.com> Hi Hangyu Hua, Thanks. I think I see the problem too. But I do wonder, is this more general than Geneve options? That is, can this occur with any sequence of options, that consume space in enc_opts (configured in fl_set_key()) that in total are more than 256 bytes? > --- > net/sched/cls_flower.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c > index e960a46b0520..a326fbfe4339 100644 > --- a/net/sched/cls_flower.c > +++ b/net/sched/cls_flower.c > @@ -1153,6 +1153,9 @@ static int fl_set_geneve_opt(const struct nlattr *nla, struct fl_flow_key *key, > if (option_len > sizeof(struct geneve_opt)) > data_len = option_len - sizeof(struct geneve_opt); > > + if (key->enc_opts.len > FLOW_DIS_TUN_OPTS_MAX - 4) > + return -ERANGE; > + > opt = (struct geneve_opt *)&key->enc_opts.data[key->enc_opts.len]; > memset(opt, 0xff, option_len); > opt->length = data_len / 4; > -- > 2.34.1 > >
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