[PATCH] net: sched: Annotate struct tc_pedit with __counted_by

[PATCH] net: sched: Annotate struct tc_pedit with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct tc_pedit.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-hardening@vger.kernel.org
---
 include/uapi/linux/tc_act/tc_pedit.h | 2 +-
 net/sched/act_pedit.c                | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/tc_act/tc_pedit.h b/include/uapi/linux/tc_act/tc_pedit.h
index f3e61b04fa01..f5cab7fc96ab 100644
--- a/include/uapi/linux/tc_act/tc_pedit.h
+++ b/include/uapi/linux/tc_act/tc_pedit.h
@@ -62,7 +62,7 @@ struct tc_pedit_sel {
 	tc_gen;
 	unsigned char           nkeys;
 	unsigned char           flags;
-	struct tc_pedit_key     keys[0];
+	struct tc_pedit_key     keys[] __counted_by(nkeys);
 };
 
 #define tc_pedit tc_pedit_sel
diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index 2ef22969f274..21e863d2898c 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -515,11 +515,11 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a,
 		spin_unlock_bh(&p->tcf_lock);
 		return -ENOBUFS;
 	}
+	opt->nkeys = parms->tcfp_nkeys;
 
 	memcpy(opt->keys, parms->tcfp_keys,
 	       flex_array_size(opt, keys, parms->tcfp_nkeys));
 	opt->index = p->tcf_index;
-	opt->nkeys = parms->tcfp_nkeys;
 	opt->flags = parms->tcfp_flags;
 	opt->action = p->tcf_action;
 	opt->refcnt = refcount_read(&p->tcf_refcnt) - ref;
-- 
2.34.1

Re: [PATCH] net: sched: Annotate struct tc_pedit with __counted_by

[Gustavo A. R. Silva]

On 2/16/24 17:27, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct tc_pedit.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> Cc: Cong Wang <xiyou.wangcong@gmail.com>
> Cc: Jiri Pirko <jiri@resnulli.us>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: netdev@vger.kernel.org
> Cc: linux-hardening@vger.kernel.org

`opt->nkeys` updated before `memcpy()`, looks good to me:

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
--
Gustavo

> ---
>   include/uapi/linux/tc_act/tc_pedit.h | 2 +-
>   net/sched/act_pedit.c                | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/tc_act/tc_pedit.h b/include/uapi/linux/tc_act/tc_pedit.h
> index f3e61b04fa01..f5cab7fc96ab 100644
> --- a/include/uapi/linux/tc_act/tc_pedit.h
> +++ b/include/uapi/linux/tc_act/tc_pedit.h
> @@ -62,7 +62,7 @@ struct tc_pedit_sel {
>   	tc_gen;
>   	unsigned char           nkeys;
>   	unsigned char           flags;
> -	struct tc_pedit_key     keys[0];
> +	struct tc_pedit_key     keys[] __counted_by(nkeys);
>   };
>   
>   #define tc_pedit tc_pedit_sel
> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
> index 2ef22969f274..21e863d2898c 100644
> --- a/net/sched/act_pedit.c
> +++ b/net/sched/act_pedit.c
> @@ -515,11 +515,11 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a,
>   		spin_unlock_bh(&p->tcf_lock);
>   		return -ENOBUFS;
>   	}
> +	opt->nkeys = parms->tcfp_nkeys;
>   
>   	memcpy(opt->keys, parms->tcfp_keys,
>   	       flex_array_size(opt, keys, parms->tcfp_nkeys));
>   	opt->index = p->tcf_index;
> -	opt->nkeys = parms->tcfp_nkeys;
>   	opt->flags = parms->tcfp_flags;
>   	opt->action = p->tcf_action;
>   	opt->refcnt = refcount_read(&p->tcf_refcnt) - ref;

Re: [PATCH] net: sched: Annotate struct tc_pedit with __counted_by

[Jamal Hadi Salim]

On Fri, Feb 16, 2024 at 7:04 PM Gustavo A. R. Silva
<gustavo@embeddedor.com> wrote:
>
>
>
> On 2/16/24 17:27, Kees Cook wrote:
> > Prepare for the coming implementation by GCC and Clang of the __counted_by
> > attribute. Flexible array members annotated with __counted_by can have
> > their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> > (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> > functions).
> >
> > As found with Coccinelle[1], add __counted_by for struct tc_pedit.
> > Additionally, since the element count member must be set before accessing
> > the annotated flexible array member, move its initialization earlier.
> >
> > Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > Cc: Jakub Kicinski <kuba@kernel.org>
> > Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> > Cc: Cong Wang <xiyou.wangcong@gmail.com>
> > Cc: Jiri Pirko <jiri@resnulli.us>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Eric Dumazet <edumazet@google.com>
> > Cc: Paolo Abeni <pabeni@redhat.com>
> > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> > Cc: netdev@vger.kernel.org
> > Cc: linux-hardening@vger.kernel.org
>
> `opt->nkeys` updated before `memcpy()`, looks good to me:
>
> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Looks good to me.
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>

cheers,
jamal

> Thanks!
> --
> Gustavo
>
> > ---
> >   include/uapi/linux/tc_act/tc_pedit.h | 2 +-
> >   net/sched/act_pedit.c                | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/tc_act/tc_pedit.h b/include/uapi/linux/tc_act/tc_pedit.h
> > index f3e61b04fa01..f5cab7fc96ab 100644
> > --- a/include/uapi/linux/tc_act/tc_pedit.h
> > +++ b/include/uapi/linux/tc_act/tc_pedit.h
> > @@ -62,7 +62,7 @@ struct tc_pedit_sel {
> >       tc_gen;
> >       unsigned char           nkeys;
> >       unsigned char           flags;
> > -     struct tc_pedit_key     keys[0];
> > +     struct tc_pedit_key     keys[] __counted_by(nkeys);
> >   };
> >
> >   #define tc_pedit tc_pedit_sel
> > diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
> > index 2ef22969f274..21e863d2898c 100644
> > --- a/net/sched/act_pedit.c
> > +++ b/net/sched/act_pedit.c
> > @@ -515,11 +515,11 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a,
> >               spin_unlock_bh(&p->tcf_lock);
> >               return -ENOBUFS;
> >       }
> > +     opt->nkeys = parms->tcfp_nkeys;
> >
> >       memcpy(opt->keys, parms->tcfp_keys,
> >              flex_array_size(opt, keys, parms->tcfp_nkeys));
> >       opt->index = p->tcf_index;
> > -     opt->nkeys = parms->tcfp_nkeys;
> >       opt->flags = parms->tcfp_flags;
> >       opt->action = p->tcf_action;
> >       opt->refcnt = refcount_read(&p->tcf_refcnt) - ref;

Re: [PATCH] net: sched: Annotate struct tc_pedit with __counted_by

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Fri, 16 Feb 2024 15:27:44 -0800 you wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct tc_pedit.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
> 
> [...]

Here is the summary with links:
  - net: sched: Annotate struct tc_pedit with __counted_by
    https://git.kernel.org/netdev/net-next/c/1e63e5a813fa

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html