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netfilter: nft_inner: Use nested-BH locking for nft_pcpu_tun_ctx

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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: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Sebastian Andrzej Siewior
2025-05-12 12:28:45 +02:00
committed by Pablo Neira Ayuso
parent a1f1acb9c5
commit ba36fada9a
1 changed files with 15 additions and 3 deletions
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18
net/netfilter/nft_inner.c
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@@ -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();
}