Commit ba36fada authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Pablo Neira Ayuso
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netfilter: nft_inner: Use nested-BH locking for nft_pcpu_tun_ctx 



nft_pcpu_tun_ctx is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.

Make a struct with a nft_inner_tun_ctx member (original
nft_pcpu_tun_ctx) and a local_lock_t and use local_lock_nested_bh() for
locking. This change adds only lockdep coverage and does not alter the
functional behaviour for !PREEMPT_RT.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent a1f1acb9

net/netfilter/nft_inner.c

+15 −3
Original line number Diff line number Diff line
@@ -23,7 +23,14 @@ 
#include <linux/ip.h>

#include <linux/ipv6.h>



static DEFINE_PER_CPU(struct nft_inner_tun_ctx, nft_pcpu_tun_ctx);

struct nft_inner_tun_ctx_locked {

	struct nft_inner_tun_ctx ctx;

	local_lock_t bh_lock;

};



static DEFINE_PER_CPU(struct nft_inner_tun_ctx_locked, nft_pcpu_tun_ctx) = {

	.bh_lock = INIT_LOCAL_LOCK(bh_lock),

};



/* Same layout as nft_expr but it embeds the private expression data area. */

struct __nft_expr {
@@ -237,12 +244,15 @@ static bool nft_inner_restore_tun_ctx(const struct nft_pktinfo *pkt, 
	struct nft_inner_tun_ctx *this_cpu_tun_ctx;



	local_bh_disable();

	this_cpu_tun_ctx = this_cpu_ptr(&nft_pcpu_tun_ctx);

	local_lock_nested_bh(&nft_pcpu_tun_ctx.bh_lock);

	this_cpu_tun_ctx = this_cpu_ptr(&nft_pcpu_tun_ctx.ctx);

	if (this_cpu_tun_ctx->cookie != (unsigned long)pkt->skb) {

		local_bh_enable();

		local_unlock_nested_bh(&nft_pcpu_tun_ctx.bh_lock);

		return false;

	}

	*tun_ctx = *this_cpu_tun_ctx;

	local_unlock_nested_bh(&nft_pcpu_tun_ctx.bh_lock);

	local_bh_enable();



	return true;
@@ -254,9 +264,11 @@ static void nft_inner_save_tun_ctx(const struct nft_pktinfo *pkt, 
	struct nft_inner_tun_ctx *this_cpu_tun_ctx;



	local_bh_disable();

	this_cpu_tun_ctx = this_cpu_ptr(&nft_pcpu_tun_ctx);

	local_lock_nested_bh(&nft_pcpu_tun_ctx.bh_lock);

	this_cpu_tun_ctx = this_cpu_ptr(&nft_pcpu_tun_ctx.ctx);

	if (this_cpu_tun_ctx->cookie != tun_ctx->cookie)

		*this_cpu_tun_ctx = *tun_ctx;

	local_unlock_nested_bh(&nft_pcpu_tun_ctx.bh_lock);

	local_bh_enable();

}