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Miller" , David Ahern , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Enke Chen , Altan Hacigumus Subject: [PATCH net] tcp: make probe0 timer handle expired user timeout Date: Mon, 13 Apr 2026 18:36:34 -0700 Message-ID: <20260414013634.43997-1-ahacigu.linux@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: 8bit tcp_clamp_probe0_to_user_timeout() computes remaining time in jiffies using subtraction with an unsigned lvalue. If elapsed probing time already exceeds the configured TCP_USER_TIMEOUT, the subtraction underflows and yields a large value. Handle this expiration case similarly to tcp_clamp_rto_to_user_timeout(). Fixes: 344db93ae3ee ("tcp: make TCP_USER_TIMEOUT accurate for zero window probes") Signed-off-by: Altan Hacigumus --- net/ipv4/tcp_timer.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 5a14a53a3c9e..4a43356a4e06 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -50,7 +50,8 @@ static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) { const struct inet_connection_sock *icsk = inet_csk(sk); - u32 remaining, user_timeout; + u32 user_timeout; + s32 remaining; s32 elapsed; user_timeout = READ_ONCE(icsk->icsk_user_timeout); @@ -61,6 +62,8 @@ u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) if (unlikely(elapsed < 0)) elapsed = 0; remaining = msecs_to_jiffies(user_timeout) - elapsed; + if (remaining <= 0) + return 1; remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); return min_t(u32, remaining, when); -- 2.43.0