From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E904ACD5BB7 for ; Thu, 21 May 2026 13:33:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DF1496B009D; Thu, 21 May 2026 09:33:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DC8DF6B009E; Thu, 21 May 2026 09:33:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CB7266B009F; Thu, 21 May 2026 09:33:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id B9EF16B009D for ; Thu, 21 May 2026 09:33:34 -0400 (EDT) Received: from smtpin09.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 7C4891C04F2 for ; Thu, 21 May 2026 13:33:34 +0000 (UTC) X-FDA: 84791519148.09.93D8CBA Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf25.hostedemail.com (Postfix) with ESMTP id B9DE9A000D for ; Thu, 21 May 2026 13:33:32 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=aURtmQtr; spf=pass (imf25.hostedemail.com: domain of kees@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1779370412; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Mj7DVCvMStdFPb34OrcUAAH1hWW4OYzU+C7hp9VpbjY=; b=wYo2wv7AzLBL9KnDI4nA/HoKb6wnUAJ2nZOjLVZlYLdopHeXpeOq/0K9ghu/tgQucKTY34 KBudiG678xHIOQ4mWhavboE3DOnzyiFyBYVaCxtrDnmgQxj8FGNFHkj2rMcpW/hLEhlm8E nMqvj/ySuxUNLD7tBGHJCvWGo8KDDeQ= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=aURtmQtr; spf=pass (imf25.hostedemail.com: domain of kees@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1779370412; a=rsa-sha256; cv=none; b=ZaUzKiNipLPnWy2rskZyFj7UqBbOCCg7WmArPqFC4rILbDYLv67Lbu+kfSFBR38xhCs7o0 N5mQCdpXF6ELq2RnrnRLXgiMZG/PLJL0nihX9Pl2DY5wlal8V4NZ51gtz4nzBkgU5nu987 1kqNo9DwEaeIVrWHUSe9b/D/EQb48G8= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 2532D44629; Thu, 21 May 2026 13:33:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFEC21F01565; Thu, 21 May 2026 13:33:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779370407; bh=Mj7DVCvMStdFPb34OrcUAAH1hWW4OYzU+C7hp9VpbjY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aURtmQtrwPk362cS1vDZGBJmbbXcm3ql47tmCQHz8PJEmKOF7/jLX6+fHXlEqbEva OwKnOcM8EQ2xhWSTSyGGYEKpHyvyEBd/6fgnNr159VVhcsbUpOC1WtyC6v/6zEJPp7 PfX1fyNcqVsrSCL7uuLFL3Ma0mOwSc/FqWMjfb2WpGH+pZhNrZwj6CgkRIxXL3YNVz gZ0zLwRhyzfV0vFW1qYm1/eyWyAnFWpN/ARSge3qfyc4+8HkcpGHlvX9JLTbOkIU23 ufiacMGKFizrGoSI31tRqHYQuHjL4WtX4qjOWurnM2F9zXlI3MXo0XHg0Hoh6hp/z6 Tk/4oaz0PA/ZA== From: Kees Cook To: Luis Chamberlain Cc: Kees Cook , Pengpeng Hou , Petr Pavlu , Richard Weinberger , Anton Ivanov , Johannes Berg , "Rafael J. Wysocki" , Len Brown , Corey Minyard , Gabriel Somlo , "Michael S. Tsirkin" , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Bart Van Assche , Jason Gunthorpe , Leon Romanovsky , Laurent Pinchart , Hans de Goede , Mauro Carvalho Chehab , Bjorn Helgaas , Hannes Reinecke , "James E.J. Bottomley" , "Martin K. Petersen" , Daniel Lezcano , Zhang Rui , Lukasz Luba , Greg Kroah-Hartman , Jiri Slaby , Alan Stern , Jason Wang , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Jason Baron , Jim Cromie , Tiwei Bie , Benjamin Berg , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , "David E. Box" , "Maciej W. Rozycki" , Srinivas Pandruvada , Peter Zijlstra , Heiko Carstens , Vasily Gorbik , Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. 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Hallyn" , Andy Shevchenko , Georgia Garcia , kvm@vger.kernel.org, dmaengine@vger.kernel.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-um@lists.infradead.org, linux-acpi@vger.kernel.org, openipmi-developer@lists.sourceforge.net, qemu-devel@nongnu.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-pci@vger.kernel.org, linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH 06/11] moduleparam: Add seq_buf-based .get callback alongside .get_str Date: Thu, 21 May 2026 06:33:19 -0700 Message-Id: <20260521133326.2465264-6-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260521133315.work.845-kees@kernel.org> References: <20260521133315.work.845-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3696; i=kees@kernel.org; h=from:subject; bh=T4N6FoAPN5e2cqvWSGS7oEs1xiLk99wdr1LKck0ur78=; b=owGbwMvMwCVmps19z/KJym7G02pJDFn8nIs2HH8iHuPEcem9X7HM2rJrS2LZVs8vP/M+reLdF K3trxtfdZSyMIhxMciKKbIE2bnHuXi8bQ93n6sIM4eVCWQIAxenAExEwZOR4alreLoXi13roV/i 9/tfrbvsVLZZb2L3Qh33TS8N1v2/U8fwT//2x1KTz9OUg91P7LvT39NrdVL4qeIHRzc9ZcnAHRc /cgAA X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B9DE9A000D X-Stat-Signature: g63mb3cncnzqyutjkzeq1x7m4tuk9p4k X-HE-Tag: 1779370412-942006 X-HE-Meta: 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 2La3pNEt sH/i7hC5B0XnTzMhuDSJfcVkGzxlFCdmAqehDKgJX7M4KqtNVqMquP5J0uaAJVPZbxsKllZDZ3Bq9C2SYDsRRvfpZ7RyiirxI/+EKJFLzTCjNC2kJC+sbVmX94LYq8K2tkStSM7tsl4w3DkBJ/UVGRXpl/DA6xd5JV47Q/EOqNGM7pNZ4mRsrZnPHLDYsh5yXAky6IuNBK490PWmnrMP0aK5umsdhaP05qFQNSEfLjKoIawmop6iPb7HxTJKrkVprwtomAxODEm4yFMfgurq4qLnAi558ELjLgHhU1JV/7d5sXdJSu3CzvRQcw5aaSc5+MrX8O2L+OXqvxB9ihev7QmgPM3jDbs3uZFVm Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add a new struct kernel_param_ops::get callback whose signature takes a struct seq_buf instead of a raw char buffer: int (*get)(struct seq_buf *sb, const struct kernel_param *kp); The previously-legacy .get field is now .get_str (char *buffer); .get is the new seq_buf-aware form. param_attr_show() prefers .get when set, otherwise falls back to .get_str. WARN_ON_ONCE() if both are set. Return contract for .get: < 0 : errno propagated to userspace; seq_buf contents discarded = 0 : success; length derived from seq_buf_used() > 0 : forbidden; the dispatcher WARN_ON_ONCE()s and treats as 0 The default policy on seq_buf_has_overflowed() is silent truncation, matching scnprintf()/sysfs_emit() behaviour. Callbacks that want a specific overflow errno can check seq_buf_has_overflowed() and return their preferred error. No callbacks use .get yet; the legacy path is still the only one in use after this commit. A subsequent commit teaches DEFINE_KERNEL_PARAM_OPS to route initializers by type. Signed-off-by: Kees Cook --- include/linux/moduleparam.h | 13 ++++++++++++- kernel/params.c | 26 ++++++++++++++++++++++++-- 2 files changed, 36 insertions(+), 3 deletions(-) diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h index f5f4148e2504..c52120f6ac28 100644 --- a/include/linux/moduleparam.h +++ b/include/linux/moduleparam.h @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -62,7 +63,17 @@ struct kernel_param_ops { unsigned int flags; /* Returns 0, or -errno. arg is in kp->arg. */ int (*set)(const char *val, const struct kernel_param *kp); - /* Returns length written or -errno. Buffer is 4k (ie. be short!) */ + /* + * Format the parameter's value into @s. Return 0 on success + * (length derived from seq_buf_used()) or -errno on error. + * Exactly one of .get and .get_str should be set; the dispatcher + * WARNs and prefers .get if both are. + */ + int (*get)(struct seq_buf *s, const struct kernel_param *kp); + /* + * Returns length written or -errno. Buffer is 4k (ie. be short!). + * Deprecated: callbacks should implement .get instead. + */ int (*get_str)(char *buffer, const struct kernel_param *kp); /* Optional function to free kp->arg when module unloaded. */ void (*free)(void *arg); diff --git a/kernel/params.c b/kernel/params.c index 6852caea1785..4eda2d23ddf2 100644 --- a/kernel/params.c +++ b/kernel/params.c @@ -553,12 +553,34 @@ static ssize_t param_attr_show(const struct module_attribute *mattr, { int count; const struct param_attribute *attribute = to_param_attr(mattr); + const struct kernel_param_ops *ops = attribute->param->ops; - if (!attribute->param->ops->get_str) + if (!ops->get && !ops->get_str) return -EPERM; + WARN_ON_ONCE(ops->get && ops->get_str); + kernel_param_lock(mk->mod); - count = attribute->param->ops->get_str(buf, attribute->param); + if (ops->get) { + struct seq_buf s; + + seq_buf_init(&s, buf, PAGE_SIZE); + count = ops->get(&s, attribute->param); + if (count >= 0) { + WARN_ON_ONCE(count > 0); + count = seq_buf_used(&s); + /* Make sure string is terminated. */ + seq_buf_str(&s); + /* + * If overflowed, reduce count by 1 for trailing + * NUL byte. + */ + if (seq_buf_has_overflowed(&s)) + count--; + } + } else { + count = ops->get_str(buf, attribute->param); + } kernel_param_unlock(mk->mod); return count; } -- 2.34.1