From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9DD123A1687; Wed, 30 Sep 2026 16:41:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790786462; cv=none; b=hJLuNxx4pAr23/2pKNR8moX30af2kBIJI0d54Gtbc763h+vENfMCM0hQdnNX6ByYQmi0DNn7Jta/6VUoUZKhknPyiOJshYWH+FBUIubRuqcBUCSI8vzpeoZXELbhYOOUOxFKTNr96MltxHyFE78WFBhFWkDT8tkZ5ncAMOCIjvs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790786462; c=relaxed/simple; bh=yN1W0VIvbM74XeHwT9Lj2NO5JBQsRkhR34wwHnKW1xM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ck7suu4hTAZ42+l7VchzKGULLR0hCsHwxQtKD2gABKrh3+u3hRikWwhCQzlBskMsTvjuCaOnpclH5ywb5BKl0vqCPX4Nt+30KY5ZPkxLw85ftjCSaMKG5FaTMrq+dT0AgQc3S4Jz2SWPdm62tFnBhkHrENlREOhaBEHgJiAsMGc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RMoFJcXW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="RMoFJcXW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A54A11F000FF; Wed, 30 Sep 2026 16:41:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790786461; bh=+G2ESI6vT++O6NV5OBRFD+LKAYLn/cP12L8qxySd2ts=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RMoFJcXWozWzWihQY2M5M1CgcR2nbxjE22B56RcHkvJ4pfX7umX4IPWXqhMqiYLkm 3zWH9MpYW43cIXxF4llX90r05ryavLl/COSl8d6HKgYQ91CsLNI8+wGpXsboBeT2qj k+0FtZivfjwT6ChhuNesT8WTdvqci4451i4YUOlI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tangxin Xie , Xin Long , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 869/982] sctp: hold asoc or transport before mod_timer() in timer handlers Date: Wed, 30 Sep 2026 17:26:45 +0200 Message-ID: <20260930152435.415947351@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xin Long [ Upstream commit cae23ae3f7887a1cf8a75da38edcebeef695040f ] Take the association or transport reference before rearming a timer in the timer handlers. The existing code calls mod_timer() before taking the reference needed by the rearmed timer without holding the sock lock. This creates a race with timer cleanup: if the timer is deleted after mod_timer() returns but before the reference is taken, the cleanup path can drop the timer's reference and destroy the transport or association. The timer handler then takes a reference on the already freed object and eventually drops it, causing a refcount underflow. Hold the object before mod_timer() and drop the reference if mod_timer() reports that the timer was already pending in timer handlers. Apply the same ordering to the proto-unreachable path, which can rearm a transport timer outside the timer handlers without holding the sock lock. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Tangxin Xie Signed-off-by: Xin Long Link: https://patch.msgid.link/c31b5e3ee2b7274e804f5eba2f21e2412e7eef7a.1790013825.git.lucien.xin@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sctp/input.c | 7 ++++--- net/sctp/sm_sideeffect.c | 37 ++++++++++++++++++++++--------------- 2 files changed, 26 insertions(+), 18 deletions(-) diff --git a/net/sctp/input.c b/net/sctp/input.c index 70530cbe57d0a..b208569b4bf0e 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -451,9 +451,10 @@ void sctp_icmp_proto_unreachable(struct sock *sk, if (timer_pending(&t->proto_unreach_timer)) return; else { - if (!mod_timer(&t->proto_unreach_timer, - jiffies + (HZ/20))) - sctp_transport_hold(t); + sctp_transport_hold(t); + if (mod_timer(&t->proto_unreach_timer, + jiffies + (HZ / 20))) + sctp_transport_put(t); } } else { struct net *net = sock_net(sk); diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c index 4391f070dc1e1..cfc35dadaf74a 100644 --- a/net/sctp/sm_sideeffect.c +++ b/net/sctp/sm_sideeffect.c @@ -244,8 +244,9 @@ void sctp_generate_t3_rtx_event(struct timer_list *t) pr_debug("%s: sock is busy\n", __func__); /* Try again later. */ - if (!mod_timer(&transport->T3_rtx_timer, jiffies + (HZ/20))) - sctp_transport_hold(transport); + sctp_transport_hold(transport); + if (mod_timer(&transport->T3_rtx_timer, jiffies + (HZ / 20))) + sctp_transport_put(transport); goto out_unlock; } @@ -280,8 +281,9 @@ static void sctp_generate_timeout_event(struct sctp_association *asoc, timeout_type); /* Try again later. */ - if (!mod_timer(&asoc->timers[timeout_type], jiffies + (HZ/20))) - sctp_association_hold(asoc); + sctp_association_hold(asoc); + if (mod_timer(&asoc->timers[timeout_type], jiffies + (HZ / 20))) + sctp_association_put(asoc); goto out_unlock; } @@ -373,8 +375,9 @@ void sctp_generate_heartbeat_event(struct timer_list *t) pr_debug("%s: sock is busy\n", __func__); /* Try again later. */ - if (!mod_timer(&transport->hb_timer, jiffies + (HZ/20))) - sctp_transport_hold(transport); + sctp_transport_hold(transport); + if (mod_timer(&transport->hb_timer, jiffies + (HZ / 20))) + sctp_transport_put(transport); goto out_unlock; } @@ -383,8 +386,9 @@ void sctp_generate_heartbeat_event(struct timer_list *t) timeout = sctp_transport_timeout(transport); if (elapsed < timeout) { elapsed = timeout - elapsed; - if (!mod_timer(&transport->hb_timer, jiffies + elapsed)) - sctp_transport_hold(transport); + sctp_transport_hold(transport); + if (mod_timer(&transport->hb_timer, jiffies + elapsed)) + sctp_transport_put(transport); goto out_unlock; } @@ -417,9 +421,10 @@ void sctp_generate_proto_unreach_event(struct timer_list *t) pr_debug("%s: sock is busy\n", __func__); /* Try again later. */ - if (!mod_timer(&transport->proto_unreach_timer, - jiffies + (HZ/20))) - sctp_transport_hold(transport); + sctp_transport_hold(transport); + if (mod_timer(&transport->proto_unreach_timer, + jiffies + (HZ / 20))) + sctp_transport_put(transport); goto out_unlock; } @@ -453,8 +458,9 @@ void sctp_generate_reconf_event(struct timer_list *t) pr_debug("%s: sock is busy\n", __func__); /* Try again later. */ - if (!mod_timer(&transport->reconf_timer, jiffies + (HZ / 20))) - sctp_transport_hold(transport); + sctp_transport_hold(transport); + if (mod_timer(&transport->reconf_timer, jiffies + (HZ / 20))) + sctp_transport_put(transport); goto out_unlock; } @@ -489,8 +495,9 @@ void sctp_generate_probe_event(struct timer_list *t) pr_debug("%s: sock is busy\n", __func__); /* Try again later. */ - if (!mod_timer(&transport->probe_timer, jiffies + (HZ / 20))) - sctp_transport_hold(transport); + sctp_transport_hold(transport); + if (mod_timer(&transport->probe_timer, jiffies + (HZ / 20))) + sctp_transport_put(transport); goto out_unlock; } -- 2.53.0