From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f71.google.com (mail-oo1-f71.google.com [209.85.161.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D578D443AA3 for ; Mon, 14 Sep 2026 11:30:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789385420; cv=none; b=sNCztVbSGNpdh1Y4FidrQCxQjbdC9rOv5s88mU5QGqS9uqWDXwMlpfulNThPw0oyNxvbK3SY6+AJstiDK1BdoXyZX8jbbJmGA3xGHFoJA/0cmVyxNuaLowMg+qGy4KXBPlyyKwbvWRLDeHPPjVI5Did/BrZd8xh+r+W3kRfFM7A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789385420; c=relaxed/simple; bh=n20Ba5LUQL7bUD+JlHlCQioYJNI0zR4FOqKw7owM7Yw=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=XB8qqyVpZns8DNDaJaayf2VN+zm+NKiuyULqgiTiiaQgSxkHmeaWdeOn2sOW9/WlmocfLRrgEBn1a4DlWQskHNzBgTAp3xSeIxmj75jgEsBBQoxW87JZKZeG/b96tRbjMMBiWZ5vnmTNZSnkxPypggz9C+VKMZGha2NOFfPR8S0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f71.google.com with SMTP id 006d021491bc7-6c324a0c0faso1708386eaf.1 for ; Mon, 14 Sep 2026 04:30:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789385417; x=1789990217; h=content-type:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=rCSx+1bt0iswccXLvZttietBc0iGWkJz4IAHt5J1XTU=; b=bTtSSf4iEk0UpEgWITx/ooEb2dl4sVHtRs1UAYqRGQ+3MXRvTG5GfZSrb2XlUpaQ/8 zgTTkLGFW/JROY4Ma5Z3RpqCTr18wiHjyKKoehhyFTDOAAne/79J1qOOAe1aiZLej9Sf D2Wj2BRq0XjhOhn4YrpX4iQM501gaJEMxI7qeNfQHHiKF+d7QKfDlFcNDYnqFcQ0mMGc y5JYHZNOkUR3B+vgdK33JXHVj+ZMoZb9A71e0JC1ee69rOy1BukMPVQDYu1aWlFYzYSk wDb5f/tX+PbiK0wqJSd367qnvScg3AOXQpq02SL8plKEvx44FUqu7HivjVY5npAmDnlk gK+A== X-Gm-Message-State: AFuF++kWjzLCJP7JLmJlgPdkJrVpIZCXTrVXgvRcu7OiPU3h+0DRrrLb /wQTZov8UNCJDePr81Nek7oYA8yws2tGzxEQLi6Jdj+MGKflm+MhosB3gXnLO1u+VtDbrWYA3Hc UKqGfDIH0QcvD7APA0+ytpoEgDIEuhoyclGtS7vWWj7sdDw3vrlG6L/NaNuY= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:81c5:b0:6b7:8415:d77e with SMTP id 006d021491bc7-6c541f45b3bmr824865eaf.41.1789385417248; Mon, 14 Sep 2026 04:30:17 -0700 (PDT) Date: Mon, 14 Sep 2026 04:30:17 -0700 In-Reply-To: <6aa316b2.f81106d8.2ab401.0014.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6aa7dac9.3aa11909.1a03b8.0083.GAE@google.com> Subject: Forwarded: [PATCH] BUG: using smp_processor_id() in preemptible code in sk_skb_reason_drop From: syzbot To: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org. *** Subject: [PATCH] BUG: using smp_processor_id() in preemptible code in sk_skb_reason_drop Author: jchuang26@m.fudan.edu.cn #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 50d05c7c76c96b90462f24debacca971d2e86713 Reported-by: syzbot+dc57fd6722deb17e92af@syzkaller.appspotmail.com diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index abaf108ac..4c068d613 100644 --- a/net/core/drop_monitor.c +++ b/net/core/drop_monitor.c @@ -516,6 +516,15 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore, */ nskb->tstamp = tstamp; + /* + * The tracepoint can run in preemptible context (e.g. from + * tcp_data_queue()). Pin the task to the current CPU before + * dereferencing the per-CPU pointer, otherwise this_cpu_ptr() + * triggers a "using smp_processor_id() in preemptible code" + * splat. migrate_disable() is used instead of preempt_disable() + * because the drop_queue spinlock can sleep on PREEMPT_RT. + */ + migrate_disable(); data = this_cpu_ptr(&dm_cpu_data); spin_lock_irqsave(&data->drop_queue.lock, flags); @@ -527,6 +536,7 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore, schedule_work(&data->dm_alert_work); + migrate_enable(); return; unlock_free: @@ -534,6 +544,7 @@ static void net_dm_packet_trace_kfree_skb_hit(void *ignore, u64_stats_inc(&data->stats.dropped); u64_stats_update_end(&data->stats.syncp); spin_unlock_irqrestore(&data->drop_queue.lock, flags); + migrate_enable(); consume_skb(nskb); }