From nobody Mon Dec 1 22:03:24 2025 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) (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 A8019305940 for ; Thu, 27 Nov 2025 19:44:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.43 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764272656; cv=none; b=YxWVR8pARZ3DC+AkO0XbUxw7kKFlx3jLshktcn94E8MeyLw8L5a7qPma9/tjPubo7MS95yTk6Qvhto1qJ8DuSCk4Yun2QNj6qofwE/fhqK9Us/3f+vT+hYEEMmI4L6gfuAEhb2iZT3ktxIwsCxpiO012mgkcb0yUiAh20frKJh4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764272656; c=relaxed/simple; bh=1CF5S9h8hQadDaF5RBnojJFx6Y/A7Dvwj62IheBuLrg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MrUGh33W09MPdXMjdmkZG4rWXUHPfLuO1An4Hi7Ca4le5CkCQLqvCyF0JTRIhJDycosb3JoU2daNAeHI/fORzQAfQcap67Yh7M7aqManPJmKiu/+HijfxwRRbZEtP4FRyQPwX/G/AhiPbpWVMiN4hExw8oV7oR8ckezUrz0wRxE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=chrisdown.name; spf=pass smtp.mailfrom=chrisdown.name; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b=stvJzWVY; arc=none smtp.client-ip=209.85.216.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=chrisdown.name Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chrisdown.name Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="stvJzWVY" Received: by mail-pj1-f43.google.com with SMTP id 98e67ed59e1d1-3437ea05540so918856a91.0 for ; Thu, 27 Nov 2025 11:44:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; t=1764272654; x=1764877454; darn=vger.kernel.org; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=h8b8yXBCRbFLyQXU1zQMEGSfAxCXFrPJdZrYjb8gf3g=; b=stvJzWVYsrPZNJwcjUuaSjbnIGvtzH5Ziul6vF/PloYuVElpSZkTHMn4I+KnOQqkCS MlF08weLhRNJFWzI6FFUDg0wBKew1VCde7VAlAm8KEdz7bYN/aUknrirEsdQQgZ+O+5z oKHIH/D6XnTyFNBRSHFb12i8Eg2scu9PsnDh0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764272654; x=1764877454; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=h8b8yXBCRbFLyQXU1zQMEGSfAxCXFrPJdZrYjb8gf3g=; b=PNdZd/lqWmkZeFDxoTv6LVHyJ3V3QnsiOLCeVcfb4Ua39RTaieN/EZxlkQ+vjS9wbK obvggKulg2JSLjbv7Woji3u6CDpjOQpNgnqzwuf5lgKoTa+4J43Lvn1WQiPmrXTgi6ek L1jbftsyzZMvwjpgBzDLh39WKA6/44NUeD6YglcPGiiy2SSJUgVWm5aD4od6Um/CT/Yv WohhRGcB4dgxYXDuiFCaKKn1e1pHZ2hJJXPtXvBAK6T1j43DtOn5bt9+qeuX6w27eDAK dkjjhL4Lw2ISg5XH0AkbMaevprgRIfIwmzkP6UeYg2RoR3PlWB5ZyUHI+o/fG8lfXs4W 8feA== X-Gm-Message-State: AOJu0Yxm8vZg+mji9tZ0uRsSBbKlDmwBHNGgVhNEUFhn7SFN0uM0ia99 /NSbhosASE1RUzT7JUxNzmvSj/jycfEdE6o99LZGfjjYiY4S6MPJNPMklQ6ef4MW3S9MLdlv1BZ y6pX5Cwd9pw== X-Gm-Gg: ASbGncvSiDM/oOIBATwL0bBTX34Dxo/00HvnIh3pZL09lxif02ivgqvB0io3wtpWOBV ueQkNOWd1pKpsUtysUGZpYhUQ2o1XBpEmJrgti+GgMwqx5Nyy9xuga3Ld4oyWV+RBaZ+SCb7HG7 YPmfBvS7A8uLbXzW4R96YTQ6KfSy/1zrxVR32WJM7lxEoSiQu9053M9GD1fkyt1fI6Br0FxCP+J CCSr351oEySyOeaJ0AA2vL79Ed62+59OgRqSAyFt6SfMazd7lQCYEk9ELNxl0ZIxrFRCd178x1V cyC9O6zyMb9vpgEeGduYXyUxqs1pFkXmJkkA1bSNE88NKksS9SuUVDNpcVsp7OdW9u0nagR0fe2 8ugbEHiIkJDrDCXBHFSj5XY1VzH89vS5qc749HQyQGN9up7skEzxPvjySiKWcsFbKj0jQHikXM2 6SmPVU2tjk X-Google-Smtp-Source: AGHT+IHOPduOYS9vOOrCmdSDg9ymb/D3fm4+5ymsp4TQNnC8wT+ITN7mKOv9zYWNd8SXQBcRdLA55A== X-Received: by 2002:a17:90b:1d52:b0:32e:64ca:e84e with SMTP id 98e67ed59e1d1-34733e74e73mr26209306a91.15.1764272654044; Thu, 27 Nov 2025 11:44:14 -0800 (PST) Received: from localhost ([116.86.198.140]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3476a7a5322sm6434985a91.12.2025.11.27.11.44.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Nov 2025 11:44:13 -0800 (PST) Date: Fri, 28 Nov 2025 03:44:10 +0800 From: Chris Down To: Petr Mladek Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Sergey Senozhatsky , Steven Rostedt , John Ogness , Geert Uytterhoeven , Tony Lindgren , kernel-team@fb.com Subject: [PATCH v8 15/21] printk: sysrq: Clamp console loglevel to valid range Message-ID: <77d1f4e89cb69b8eb45e118cea1383a8f577f704.1764272407.git.chris@chrisdown.name> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.15 (2b349c5e) (2025-10-02) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The sysrq loglevel handler (keys 0-9) directly assigns the numeric key value to console_loglevel without any validation. This creates an inconsistency with other interfaces: the new kernel.console_loglevel sysctl, the per-console sysfs loglevel interface, and the SYSLOG_ACTION_CONSOLE_LEVEL syslog command all clamp or reject values outside the valid range. In particular, sysrq 0 sets console_loglevel to 0 (LOGLEVEL_EMERG), which is problematic because: 1. LOGLEVEL_EMERG (0) is reserved for emergency messages that should always reach all consoles. Setting console_loglevel to 0 would mean only KERN_EMERG messages print, which is likely never intended. 2. The per-console loglevel infrastructure explicitly rejects level 0 for this reason, creating an inconsistency where sysrq can set a value that other interfaces refuse. 3. CONSOLE_LOGLEVEL_MIN is defined as 1, indicating the minimum valid console loglevel, yet sysrq ignores this. Similarly, sysrq 9 sets console_loglevel to 9, which is above LOGLEVEL_DEBUG (7) and serves no useful purpose since no messages have a level that high. Use console_clamp_loglevel() to clamp the requested loglevel to the valid range [1, 8]. This ensures consistent behaviour across all loglevel-setting interfaces. Signed-off-by: Chris Down --- drivers/tty/sysrq.c | 2 +- include/linux/printk.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 1d5ae9997e79..e9d97ec28432 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -101,7 +101,7 @@ __setup("sysrq_always_enabled", sysrq_always_enabled_se= tup); =20 static void sysrq_handle_loglevel(u8 key) { - u8 loglevel =3D key - '0'; + u8 loglevel =3D console_clamp_loglevel(key - '0'); =20 console_loglevel =3D CONSOLE_LOGLEVEL_DEFAULT; pr_info("Loglevel set to %u\n", loglevel); diff --git a/include/linux/printk.h b/include/linux/printk.h index 0aa8cb8ddc09..5a8c4aca729f 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -65,6 +65,7 @@ static inline const char *printk_skip_headers(const char = *buffer) int match_devname_and_update_preferred_console(const char *match, const char *name, const short idx); +int console_clamp_loglevel(int level); =20 extern int console_printk[]; =20 --=20 2.51.2