[Patch net] cls_flower: call nla_ok() before nla_next()

[Patch net] cls_flower: call nla_ok() before nla_next()

[Cong Wang]

From: Cong Wang <cong.wang@bytedance.com>

fl_set_enc_opt() simply checks if there are still bytes left to parse,
but this is not sufficent as syzbot seems to be able to generate
malformatted netlink messages. nla_ok() is more strict so should be
used to validate the next nlattr here.

And nla_validate_nested_deprecated() has less strict check too, it is
probably too late to switch to the strict version, but we can just
call nla_ok() too after it.

Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
---
 net/sched/cls_flower.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index 1319986693fc..e265c443536e 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 
 		nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
 		msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
+		if (!nla_ok(nla_opt_msk, msk_depth))
+			return -EINVAL;
 	}
 
 	nla_for_each_attr(nla_opt_key, nla_enc_key,
@@ -1308,7 +1310,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 				return -EINVAL;
 			}
 
-			if (msk_depth)
+			if (nla_ok(nla_opt_msk, msk_depth))
 				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
 			break;
 		case TCA_FLOWER_KEY_ENC_OPTS_VXLAN:
@@ -1341,7 +1343,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 				return -EINVAL;
 			}
 
-			if (msk_depth)
+			if (nla_ok(nla_opt_msk, msk_depth))
 				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
 			break;
 		case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
@@ -1374,7 +1376,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 				return -EINVAL;
 			}
 
-			if (msk_depth)
+			if (nla_ok(nla_opt_msk, msk_depth))
 				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
 			break;
 		default:
-- 
2.25.1

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Xin Long]

On Tue, Jan 12, 2021 at 10:56 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> From: Cong Wang <cong.wang@bytedance.com>
>
> fl_set_enc_opt() simply checks if there are still bytes left to parse,
> but this is not sufficent as syzbot seems to be able to generate
> malformatted netlink messages. nla_ok() is more strict so should be
> used to validate the next nlattr here.
>
> And nla_validate_nested_deprecated() has less strict check too, it is
> probably too late to switch to the strict version, but we can just
> call nla_ok() too after it.
>
> Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> Cc: Xin Long <lucien.xin@gmail.com>
> Cc: Jiri Pirko <jiri@resnulli.us>
> Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> ---
>  net/sched/cls_flower.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> index 1319986693fc..e265c443536e 100644
> --- a/net/sched/cls_flower.c
> +++ b/net/sched/cls_flower.c
> @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
>
>                 nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
>                 msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> +               if (!nla_ok(nla_opt_msk, msk_depth))
> +                       return -EINVAL;
>         }
I think it's better to also add  NL_SET_ERR_MSG(extack, xxxx);
for this error return, like all the other places in this function.

>
>         nla_for_each_attr(nla_opt_key, nla_enc_key,
> @@ -1308,7 +1310,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
>                                 return -EINVAL;
>                         }
>
> -                       if (msk_depth)
> +                       if (nla_ok(nla_opt_msk, msk_depth))
>                                 nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
>                         break;
>                 case TCA_FLOWER_KEY_ENC_OPTS_VXLAN:
> @@ -1341,7 +1343,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
>                                 return -EINVAL;
>                         }
>
> -                       if (msk_depth)
> +                       if (nla_ok(nla_opt_msk, msk_depth))
>                                 nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
>                         break;
>                 case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
> @@ -1374,7 +1376,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
>                                 return -EINVAL;
>                         }
>
> -                       if (msk_depth)
> +                       if (nla_ok(nla_opt_msk, msk_depth))
>                                 nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
>                         break;
>                 default:
> --
> 2.25.1
>

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Cong Wang]

On Tue, Jan 12, 2021 at 3:52 AM Xin Long <lucien.xin@gmail.com> wrote:
>
> On Tue, Jan 12, 2021 at 10:56 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> >
> > From: Cong Wang <cong.wang@bytedance.com>
> >
> > fl_set_enc_opt() simply checks if there are still bytes left to parse,
> > but this is not sufficent as syzbot seems to be able to generate
> > malformatted netlink messages. nla_ok() is more strict so should be
> > used to validate the next nlattr here.
> >
> > And nla_validate_nested_deprecated() has less strict check too, it is
> > probably too late to switch to the strict version, but we can just
> > call nla_ok() too after it.
> >
> > Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> > Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> > Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> > Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> > Cc: Xin Long <lucien.xin@gmail.com>
> > Cc: Jiri Pirko <jiri@resnulli.us>
> > Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> > ---
> >  net/sched/cls_flower.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> > index 1319986693fc..e265c443536e 100644
> > --- a/net/sched/cls_flower.c
> > +++ b/net/sched/cls_flower.c
> > @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> >
> >                 nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> >                 msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > +               if (!nla_ok(nla_opt_msk, msk_depth))
> > +                       return -EINVAL;
> >         }
> I think it's better to also add  NL_SET_ERR_MSG(extack, xxxx);
> for this error return, like all the other places in this function.

I think ext message is primarily for end users who usually can not
generate malformat netlink messages.

On the other hand, the nla_validate_nested_deprecated() right above
the quoted code does not set ext message either.

Thanks.

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Jakub Kicinski]

On Mon, 11 Jan 2021 18:55:48 -0800 Cong Wang wrote:
> From: Cong Wang <cong.wang@bytedance.com>
> 
> fl_set_enc_opt() simply checks if there are still bytes left to parse,
> but this is not sufficent as syzbot seems to be able to generate
> malformatted netlink messages. nla_ok() is more strict so should be
> used to validate the next nlattr here.
> 
> And nla_validate_nested_deprecated() has less strict check too, it is
> probably too late to switch to the strict version, but we can just
> call nla_ok() too after it.
> 
> Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> Cc: Xin Long <lucien.xin@gmail.com>
> Cc: Jiri Pirko <jiri@resnulli.us>
> Signed-off-by: Cong Wang <cong.wang@bytedance.com>

Thanks for keeping up with the syzbot bugs!

> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> index 1319986693fc..e265c443536e 100644
> --- a/net/sched/cls_flower.c
> +++ b/net/sched/cls_flower.c
> @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
>  
>  		nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
>  		msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> +		if (!nla_ok(nla_opt_msk, msk_depth))
> +			return -EINVAL;

Can we just add another call to nla_validate_nested_deprecated() 
here instead of having to worry about each attr individually?
See below..

>  	}
>  
>  	nla_for_each_attr(nla_opt_key, nla_enc_key,
> @@ -1308,7 +1310,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
>  				return -EINVAL;
>  			}
>  
> -			if (msk_depth)
> +			if (nla_ok(nla_opt_msk, msk_depth))
>  				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);

Should we not error otherwise? if msk_depth && !nla_ok() then the
message is clearly misformatted. If we don't error out we'll keep
reusing the same mask over and over, while the intention of this 
code was to have mask per key AFAICT.

>  			break;
>  		case TCA_FLOWER_KEY_ENC_OPTS_VXLAN:

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Xin Long]

On Wed, Jan 13, 2021 at 1:43 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> On Tue, Jan 12, 2021 at 3:52 AM Xin Long <lucien.xin@gmail.com> wrote:
> >
> > On Tue, Jan 12, 2021 at 10:56 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > >
> > > From: Cong Wang <cong.wang@bytedance.com>
> > >
> > > fl_set_enc_opt() simply checks if there are still bytes left to parse,
> > > but this is not sufficent as syzbot seems to be able to generate
> > > malformatted netlink messages. nla_ok() is more strict so should be
> > > used to validate the next nlattr here.
> > >
> > > And nla_validate_nested_deprecated() has less strict check too, it is
> > > probably too late to switch to the strict version, but we can just
> > > call nla_ok() too after it.
> > >
> > > Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> > > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> > > Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> > > Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> > > Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> > > Cc: Xin Long <lucien.xin@gmail.com>
> > > Cc: Jiri Pirko <jiri@resnulli.us>
> > > Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> > > ---
> > >  net/sched/cls_flower.c | 8 +++++---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> > > index 1319986693fc..e265c443536e 100644
> > > --- a/net/sched/cls_flower.c
> > > +++ b/net/sched/cls_flower.c
> > > @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > >
> > >                 nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > >                 msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > > +               if (!nla_ok(nla_opt_msk, msk_depth))
> > > +                       return -EINVAL;
> > >         }
> > I think it's better to also add  NL_SET_ERR_MSG(extack, xxxx);
> > for this error return, like all the other places in this function.
>
> I think ext message is primarily for end users who usually can not
> generate malformat netlink messages.
>
> On the other hand, the nla_validate_nested_deprecated() right above
> the quoted code does not set ext message either.
nla_validate_nested_deprecated(..., extack), it's already done inside
when returns error, no?

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Cong Wang]

On Tue, Jan 12, 2021 at 5:38 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Mon, 11 Jan 2021 18:55:48 -0800 Cong Wang wrote:
> > From: Cong Wang <cong.wang@bytedance.com>
> >
> > fl_set_enc_opt() simply checks if there are still bytes left to parse,
> > but this is not sufficent as syzbot seems to be able to generate
> > malformatted netlink messages. nla_ok() is more strict so should be
> > used to validate the next nlattr here.
> >
> > And nla_validate_nested_deprecated() has less strict check too, it is
> > probably too late to switch to the strict version, but we can just
> > call nla_ok() too after it.
> >
> > Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> > Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> > Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> > Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> > Cc: Xin Long <lucien.xin@gmail.com>
> > Cc: Jiri Pirko <jiri@resnulli.us>
> > Signed-off-by: Cong Wang <cong.wang@bytedance.com>
>
> Thanks for keeping up with the syzbot bugs!
>
> > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> > index 1319986693fc..e265c443536e 100644
> > --- a/net/sched/cls_flower.c
> > +++ b/net/sched/cls_flower.c
> > @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> >
> >               nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> >               msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > +             if (!nla_ok(nla_opt_msk, msk_depth))
> > +                     return -EINVAL;
>
> Can we just add another call to nla_validate_nested_deprecated()
> here instead of having to worry about each attr individually?

No, we can not parse the nested attr here because different key types
have different attributes.

> See below..
>
> >       }
> >
> >       nla_for_each_attr(nla_opt_key, nla_enc_key,
> > @@ -1308,7 +1310,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> >                               return -EINVAL;
> >                       }
> >
> > -                     if (msk_depth)
> > +                     if (nla_ok(nla_opt_msk, msk_depth))
> >                               nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
>
> Should we not error otherwise? if msk_depth && !nla_ok() then the
> message is clearly misformatted. If we don't error out we'll keep
> reusing the same mask over and over, while the intention of this
> code was to have mask per key AFAICT.

Yeah, erroring out sounds better. Will change this in v2.

Thanks!

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Cong Wang]

On Tue, Jan 12, 2021 at 6:22 PM Xin Long <lucien.xin@gmail.com> wrote:
>
> On Wed, Jan 13, 2021 at 1:43 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> >
> > On Tue, Jan 12, 2021 at 3:52 AM Xin Long <lucien.xin@gmail.com> wrote:
> > >
> > > On Tue, Jan 12, 2021 at 10:56 AM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > > >
> > > > From: Cong Wang <cong.wang@bytedance.com>
> > > >
> > > > fl_set_enc_opt() simply checks if there are still bytes left to parse,
> > > > but this is not sufficent as syzbot seems to be able to generate
> > > > malformatted netlink messages. nla_ok() is more strict so should be
> > > > used to validate the next nlattr here.
> > > >
> > > > And nla_validate_nested_deprecated() has less strict check too, it is
> > > > probably too late to switch to the strict version, but we can just
> > > > call nla_ok() too after it.
> > > >
> > > > Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> > > > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> > > > Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> > > > Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> > > > Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> > > > Cc: Xin Long <lucien.xin@gmail.com>
> > > > Cc: Jiri Pirko <jiri@resnulli.us>
> > > > Signed-off-by: Cong Wang <cong.wang@bytedance.com>
> > > > ---
> > > >  net/sched/cls_flower.c | 8 +++++---
> > > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> > > > index 1319986693fc..e265c443536e 100644
> > > > --- a/net/sched/cls_flower.c
> > > > +++ b/net/sched/cls_flower.c
> > > > @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > > >
> > > >                 nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > > >                 msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > > > +               if (!nla_ok(nla_opt_msk, msk_depth))
> > > > +                       return -EINVAL;
> > > >         }
> > > I think it's better to also add  NL_SET_ERR_MSG(extack, xxxx);
> > > for this error return, like all the other places in this function.
> >
> > I think ext message is primarily for end users who usually can not
> > generate malformat netlink messages.
> >
> > On the other hand, the nla_validate_nested_deprecated() right above
> > the quoted code does not set ext message either.
> nla_validate_nested_deprecated(..., extack), it's already done inside
> when returns error, no?

Yeah, seems fair.

Thanks.

Re: [Patch net] cls_flower: call nla_ok() before nla_next()

[Jakub Kicinski]

On Wed, 13 Jan 2021 23:20:24 -0800 Cong Wang wrote:
> On Tue, Jan 12, 2021 at 5:38 PM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > On Mon, 11 Jan 2021 18:55:48 -0800 Cong Wang wrote:  
> > > From: Cong Wang <cong.wang@bytedance.com>
> > >
> > > fl_set_enc_opt() simply checks if there are still bytes left to parse,
> > > but this is not sufficent as syzbot seems to be able to generate
> > > malformatted netlink messages. nla_ok() is more strict so should be
> > > used to validate the next nlattr here.
> > >
> > > And nla_validate_nested_deprecated() has less strict check too, it is
> > > probably too late to switch to the strict version, but we can just
> > > call nla_ok() too after it.
> > >
> > > Reported-and-tested-by: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
> > > Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> > > Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> > > Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
> > > Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> > > Cc: Xin Long <lucien.xin@gmail.com>
> > > Cc: Jiri Pirko <jiri@resnulli.us>
> > > Signed-off-by: Cong Wang <cong.wang@bytedance.com>  
> >
> > Thanks for keeping up with the syzbot bugs!
> >  
> > > diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> > > index 1319986693fc..e265c443536e 100644
> > > --- a/net/sched/cls_flower.c
> > > +++ b/net/sched/cls_flower.c
> > > @@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > >
> > >               nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > >               msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
> > > +             if (!nla_ok(nla_opt_msk, msk_depth))
> > > +                     return -EINVAL;  
> >
> > Can we just add another call to nla_validate_nested_deprecated()
> > here instead of having to worry about each attr individually?  
> 
> No, we can not parse the nested attr here because different key types
> have different attributes.

Not parse, just validate. Policy can be NULL, then nla_validate
basically only checks nla_ok(). But my previous suggestion to call 
nla_validate_nested_deprecated() would not work, we'd need 
__nla_validate(NL_VALIDATE_TRAILING), so yeah, maybe that's more
complex for a read to understand than just calling nla_ok()...