netdev - [PATCH 14/14] net: sched: Annotate struct tc_pedit with __counted

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Date: Fri, 22 Sep 2023 10:28:56 -0700
From: Kees Cook <keescook@...omium.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Jiri Pirko <jiri@...nulli.us>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	David Ahern <dsahern@...nel.org>,
	Martin KaFai Lau <martin.lau@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Yisen Zhuang <yisen.zhuang@...wei.com>,
	Salil Mehta <salil.mehta@...wei.com>,
	Claudiu Manoil <claudiu.manoil@....com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Long Li <longli@...rosoft.com>,
	Ajay Sharma <sharmaajay@...rosoft.com>,
	Alex Elder <elder@...nel.org>,
	Pravin B Shelar <pshelar@....org>,
	Shaokun Zhang <zhangshaokun@...ilicon.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Tom Rix <trix@...hat.com>,
	Simon Horman <horms@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	linux-rdma@...r.kernel.org,
	dev@...nvswitch.org,
	linux-parisc@...r.kernel.org,
	llvm@...ts.linux.dev,
	linux-hardening@...r.kernel.org
Subject: [PATCH 14/14] net: sched: Annotate struct tc_pedit with __counted_by

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.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Jamal Hadi Salim <jhs@...atatu.com>
Cc: Cong Wang <xiyou.wangcong@...il.com>
Cc: Jiri Pirko <jiri@...nulli.us>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 net/sched/act_pedit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index 1ef8fcfa9997..77c407eff3b0 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