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Message-ID: <e9925aef-fefc-24b9-dea3-bd3bcca01b35@gmail.com> Date: Wed, 31 May 2023 13:38:49 +0800 From: Hangyu Hua <hbh25y@...il.com> To: Simon Horman <simon.horman@...igine.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() On 30/5/2023 19:36, Simon Horman wrote: > [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? > I think you are right. It is a good idea to add check in fl_set_vxlan_opt and fl_set_erspan_opt and fl_set_gtp_opt too. But they should be submitted as other patches. fl_set_geneve_opt has already check this with the following code: static int fl_set_geneve_opt(const struct nlattr *nla, struct fl_flow_key *key, int depth, int option_len, struct netlink_ext_ack *extack) { ... if (new_len > FLOW_DIS_TUN_OPTS_MAX) { NL_SET_ERR_MSG(extack, "Tunnel options exceeds max size"); return -ERANGE; } ... } This bug will only be triggered under this special condition(key->enc_opts.len = 252). So I think it will be better understood by submitting this patch independently. By the way, I think memset's third param should be option_len in fl_set_vxlan_opt and fl_set_erspan_opt. Do I need to submit another patch to fix all these issues? Thanks, Hangyu >> --- >> 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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