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([165.85.67.147]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b8dbf184e5dsm1058051366b.43.2026.02.03.05.49.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Feb 2026 05:49:10 -0800 (PST) From: anders.grahn@gmail.com To: Pablo Neira Ayuso , Florian Westphal , Phil Sutter , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Sebastian Andrzej Siewior Cc: Anders Grahn , linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org Subject: [PATCH v3] netfilter: nft_counter: Fix reset of counters on 32bit archs Date: Tue, 3 Feb 2026 14:48:30 +0100 Message-ID: <20260203134831.1205444-1-anders.grahn@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Anders Grahn nft_counter_reset() calls u64_stats_add() with a negative value to reset the counter. This will work on 64bit archs, hence the negative value added will wrap as a 64bit value which then can wrap the stat counter as well. On 32bit archs, the added negative value will wrap as a 32bit value and _not_ wrapping the stat counter properly. In most cases, this would just lead to a very large 32bit value being added to the stat counter. Fix by introducing u64_stats_sub(). Fixes: 4a1d3acd6ea8 ("netfilter: nft_counter: Use u64_stats_t for statistic= .") Signed-off-by: Anders Grahn --- include/linux/u64_stats_sync.h | 10 ++++++++++ net/netfilter/nft_counter.c | 4 ++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h index 457879938fc1..3366090a86bd 100644 --- a/include/linux/u64_stats_sync.h +++ b/include/linux/u64_stats_sync.h @@ -89,6 +89,11 @@ static inline void u64_stats_add(u64_stats_t *p, unsigne= d long val) local64_add(val, &p->v); } =20 +static inline void u64_stats_sub(u64_stats_t *p, s64 val) +{ + local64_sub(val, &p->v); +} + static inline void u64_stats_inc(u64_stats_t *p) { local64_inc(&p->v); @@ -130,6 +135,11 @@ static inline void u64_stats_add(u64_stats_t *p, unsig= ned long val) p->v +=3D val; } =20 +static inline void u64_stats_sub(u64_stats_t *p, s64 val) +{ + p->v -=3D val; +} + static inline void u64_stats_inc(u64_stats_t *p) { p->v++; diff --git a/net/netfilter/nft_counter.c b/net/netfilter/nft_counter.c index cc7325329496..0d70325280cc 100644 --- a/net/netfilter/nft_counter.c +++ b/net/netfilter/nft_counter.c @@ -117,8 +117,8 @@ static void nft_counter_reset(struct nft_counter_percpu= _priv *priv, nft_sync =3D this_cpu_ptr(&nft_counter_sync); =20 u64_stats_update_begin(nft_sync); - u64_stats_add(&this_cpu->packets, -total->packets); - u64_stats_add(&this_cpu->bytes, -total->bytes); + u64_stats_sub(&this_cpu->packets, total->packets); + u64_stats_sub(&this_cpu->bytes, total->bytes); u64_stats_update_end(nft_sync); =20 local_bh_enable(); --=20 2.43.0