* [Patch net v2] cls_flower: call nla_ok() before nla_next()
@ 2021-01-14 16:38 Cong Wang
2021-01-14 18:38 ` Jakub Kicinski
0 siblings, 1 reply; 6+ messages in thread
From: Cong Wang @ 2021-01-14 16:38 UTC (permalink / raw)
To: netdev
Cc: Cong Wang, syzbot+2624e3778b18fc497c92, Jamal Hadi Salim,
Xin Long, Jiri Pirko, Jakub Kicinski
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: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
---
net/sched/cls_flower.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index 1319986693fc..740d9018e45f 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1272,6 +1272,10 @@ 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)) {
+ NL_SET_ERR_MSG(extack, "Invalid attribute for masks");
+ return -EINVAL;
+ }
}
nla_for_each_attr(nla_opt_key, nla_enc_key,
@@ -1307,9 +1311,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
return -EINVAL;
}
-
- if (msk_depth)
- nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
break;
case TCA_FLOWER_KEY_ENC_OPTS_VXLAN:
if (key->enc_opts.dst_opt_type) {
@@ -1340,9 +1341,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
return -EINVAL;
}
-
- if (msk_depth)
- nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
break;
case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
if (key->enc_opts.dst_opt_type) {
@@ -1373,14 +1371,17 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
return -EINVAL;
}
-
- if (msk_depth)
- nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
break;
default:
NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
return -EINVAL;
}
+
+ if (!nla_ok(nla_opt_msk, msk_depth)) {
+ NL_SET_ERR_MSG(extack, "Mask attribute is invalid");
+ return -EINVAL;
+ }
+ nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
}
return 0;
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [Patch net v2] cls_flower: call nla_ok() before nla_next()
2021-01-14 16:38 [Patch net v2] cls_flower: call nla_ok() before nla_next() Cong Wang
@ 2021-01-14 18:38 ` Jakub Kicinski
2021-01-14 20:03 ` Cong Wang
0 siblings, 1 reply; 6+ messages in thread
From: Jakub Kicinski @ 2021-01-14 18:38 UTC (permalink / raw)
To: Cong Wang
Cc: netdev, Cong Wang, syzbot+2624e3778b18fc497c92, Jamal Hadi Salim,
Xin Long, Jiri Pirko
On Thu, 14 Jan 2021 08:38:22 -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")
> @@ -1340,9 +1341,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> return -EINVAL;
> }
> -
> - if (msk_depth)
> - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> break;
> case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
> if (key->enc_opts.dst_opt_type) {
> @@ -1373,14 +1371,17 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> return -EINVAL;
> }
> -
> - if (msk_depth)
> - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> break;
> default:
> NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
> return -EINVAL;
> }
> +
> + if (!nla_ok(nla_opt_msk, msk_depth)) {
> + NL_SET_ERR_MSG(extack, "Mask attribute is invalid");
> + return -EINVAL;
> + }
> + nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
we lost the if (msk_depth) now, nla_opt_msk may be NULL -
neither nla_ok() nor nla_next() take NULL
> }
>
> return 0;
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Patch net v2] cls_flower: call nla_ok() before nla_next()
2021-01-14 18:38 ` Jakub Kicinski
@ 2021-01-14 20:03 ` Cong Wang
2021-01-14 20:16 ` Jakub Kicinski
0 siblings, 1 reply; 6+ messages in thread
From: Cong Wang @ 2021-01-14 20:03 UTC (permalink / raw)
To: Jakub Kicinski
Cc: Linux Kernel Network Developers, Cong Wang, syzbot,
Jamal Hadi Salim, Xin Long, Jiri Pirko
On Thu, Jan 14, 2021 at 10:38 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Thu, 14 Jan 2021 08:38:22 -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")
>
> > @@ -1340,9 +1341,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> > return -EINVAL;
> > }
> > -
> > - if (msk_depth)
> > - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > break;
> > case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
> > if (key->enc_opts.dst_opt_type) {
> > @@ -1373,14 +1371,17 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> > return -EINVAL;
> > }
> > -
> > - if (msk_depth)
> > - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > break;
> > default:
> > NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
> > return -EINVAL;
> > }
> > +
> > + if (!nla_ok(nla_opt_msk, msk_depth)) {
> > + NL_SET_ERR_MSG(extack, "Mask attribute is invalid");
> > + return -EINVAL;
> > + }
> > + nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
>
> we lost the if (msk_depth) now, nla_opt_msk may be NULL -
> neither nla_ok() nor nla_next() take NULL
How is "if (msk_depth)" lost when nla_ok() has a stricter one?
1156 static inline int nla_ok(const struct nlattr *nla, int remaining)
1157 {
1158 return remaining >= (int) sizeof(*nla) &&
1159 nla->nla_len >= sizeof(*nla) &&
1160 nla->nla_len <= remaining;
1161 }
Line 1156 assures msk_depth is not only non-zero but also larger
than the nla struct size, and clearly nla won't be dereferenced unless
this check is passed.
I guess you mean we should not error out for nla_opt_msk==NULL
case as masks are optional?
Thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Patch net v2] cls_flower: call nla_ok() before nla_next()
2021-01-14 20:03 ` Cong Wang
@ 2021-01-14 20:16 ` Jakub Kicinski
2021-01-14 20:24 ` Cong Wang
0 siblings, 1 reply; 6+ messages in thread
From: Jakub Kicinski @ 2021-01-14 20:16 UTC (permalink / raw)
To: Cong Wang
Cc: Linux Kernel Network Developers, Cong Wang, syzbot,
Jamal Hadi Salim, Xin Long, Jiri Pirko
On Thu, 14 Jan 2021 12:03:16 -0800 Cong Wang wrote:
> On Thu, Jan 14, 2021 at 10:38 AM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > On Thu, 14 Jan 2021 08:38:22 -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")
> >
> > > @@ -1340,9 +1341,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > > NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> > > return -EINVAL;
> > > }
> > > -
> > > - if (msk_depth)
> > > - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > > break;
> > > case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
> > > if (key->enc_opts.dst_opt_type) {
> > > @@ -1373,14 +1371,17 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > > NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> > > return -EINVAL;
> > > }
> > > -
> > > - if (msk_depth)
> > > - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > > break;
> > > default:
> > > NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
> > > return -EINVAL;
> > > }
> > > +
> > > + if (!nla_ok(nla_opt_msk, msk_depth)) {
> > > + NL_SET_ERR_MSG(extack, "Mask attribute is invalid");
> > > + return -EINVAL;
> > > + }
> > > + nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> >
> > we lost the if (msk_depth) now, nla_opt_msk may be NULL -
> > neither nla_ok() nor nla_next() take NULL
>
> How is "if (msk_depth)" lost when nla_ok() has a stricter one?
>
> 1156 static inline int nla_ok(const struct nlattr *nla, int remaining)
> 1157 {
> 1158 return remaining >= (int) sizeof(*nla) &&
> 1159 nla->nla_len >= sizeof(*nla) &&
> 1160 nla->nla_len <= remaining;
> 1161 }
>
> Line 1156 assures msk_depth is not only non-zero but also larger
> than the nla struct size, and clearly nla won't be dereferenced unless
> this check is passed.
Fair, depth will but 0 so first check already fails, but nla_next()
would crash since it tries to access the length of the attribute
unconditionally.
> I guess you mean we should not error out for nla_opt_msk==NULL
> case as masks are optional?
Yup.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Patch net v2] cls_flower: call nla_ok() before nla_next()
2021-01-14 20:16 ` Jakub Kicinski
@ 2021-01-14 20:24 ` Cong Wang
2021-01-14 20:27 ` Jakub Kicinski
0 siblings, 1 reply; 6+ messages in thread
From: Cong Wang @ 2021-01-14 20:24 UTC (permalink / raw)
To: Jakub Kicinski
Cc: Linux Kernel Network Developers, Cong Wang, syzbot,
Jamal Hadi Salim, Xin Long, Jiri Pirko
On Thu, Jan 14, 2021 at 12:16 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Thu, 14 Jan 2021 12:03:16 -0800 Cong Wang wrote:
> > On Thu, Jan 14, 2021 at 10:38 AM Jakub Kicinski <kuba@kernel.org> wrote:
> > >
> > > On Thu, 14 Jan 2021 08:38:22 -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")
> > >
> > > > @@ -1340,9 +1341,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > > > NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> > > > return -EINVAL;
> > > > }
> > > > -
> > > > - if (msk_depth)
> > > > - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > > > break;
> > > > case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
> > > > if (key->enc_opts.dst_opt_type) {
> > > > @@ -1373,14 +1371,17 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
> > > > NL_SET_ERR_MSG(extack, "Key and mask miss aligned");
> > > > return -EINVAL;
> > > > }
> > > > -
> > > > - if (msk_depth)
> > > > - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > > > break;
> > > > default:
> > > > NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
> > > > return -EINVAL;
> > > > }
> > > > +
> > > > + if (!nla_ok(nla_opt_msk, msk_depth)) {
> > > > + NL_SET_ERR_MSG(extack, "Mask attribute is invalid");
> > > > + return -EINVAL;
> > > > + }
> > > > + nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> > >
> > > we lost the if (msk_depth) now, nla_opt_msk may be NULL -
> > > neither nla_ok() nor nla_next() take NULL
> >
> > How is "if (msk_depth)" lost when nla_ok() has a stricter one?
> >
> > 1156 static inline int nla_ok(const struct nlattr *nla, int remaining)
> > 1157 {
> > 1158 return remaining >= (int) sizeof(*nla) &&
> > 1159 nla->nla_len >= sizeof(*nla) &&
> > 1160 nla->nla_len <= remaining;
> > 1161 }
> >
> > Line 1156 assures msk_depth is not only non-zero but also larger
> > than the nla struct size, and clearly nla won't be dereferenced unless
> > this check is passed.
>
> Fair, depth will but 0 so first check already fails, but nla_next()
> would crash since it tries to access the length of the attribute
> unconditionally.
nla_next() is only called when nla_ok() returns true, which is not
the case for msk_depth==0, therefore NULL won't crash here.
The only problem is we become too strict to reject optionally missing
masks, we should not even call nla_ok() here, otherwise it would
break user-space. So,
+ if (!nla_opt_msk)
+ continue;
Thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Patch net v2] cls_flower: call nla_ok() before nla_next()
2021-01-14 20:24 ` Cong Wang
@ 2021-01-14 20:27 ` Jakub Kicinski
0 siblings, 0 replies; 6+ messages in thread
From: Jakub Kicinski @ 2021-01-14 20:27 UTC (permalink / raw)
To: Cong Wang
Cc: Linux Kernel Network Developers, Cong Wang, syzbot,
Jamal Hadi Salim, Xin Long, Jiri Pirko
On Thu, 14 Jan 2021 12:24:19 -0800 Cong Wang wrote:
> > Fair, depth will but 0 so first check already fails, but nla_next()
> > would crash since it tries to access the length of the attribute
> > unconditionally.
>
> nla_next() is only called when nla_ok() returns true, which is not
> the case for msk_depth==0, therefore NULL won't crash here.
>
> The only problem is we become too strict to reject optionally missing
> masks, we should not even call nla_ok() here, otherwise it would
> break user-space. So,
>
> + if (!nla_opt_msk)
> + continue;
>
> Thanks.
You're right.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-01-14 20:28 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2021-01-14 16:38 [Patch net v2] cls_flower: call nla_ok() before nla_next() Cong Wang
2021-01-14 18:38 ` Jakub Kicinski
2021-01-14 20:03 ` Cong Wang
2021-01-14 20:16 ` Jakub Kicinski
2021-01-14 20:24 ` Cong Wang
2021-01-14 20:27 ` Jakub Kicinski
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