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 B958A3C1400; Tue, 21 Jul 2026 22:38:39 +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=1784673520; cv=none; b=gziPTOocZvAvyfLrkZgAtJsl9Xv3WwsdZOAUZuUn9sPV4Az2K+ZpR0wv+gg+bK7mjU54nZG3LwfdAx/b2Z6xRfLionYt6sdRzdhbG+QvgUnwXJnVWFkeHqiu/EoTbeyLnQZNnMO53jHGZa3eJ9U6AtC7pGvEDPKYgHOCyIrQebY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784673520; c=relaxed/simple; bh=kMp7vHTE3BJ02Va0Hrs0onDCpFlgeSNHdZGHC37mBN0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OcoRETsfmnK+ZI7CJN7m9gKnKnMrOJ3wVZXWTDQGhVaReA0bgNgyG1MKJ3hfPy1bJUdjpVOxG1UH/Gee9l0IsOcdyguJqUgjeuFQT6DD2jlia7KAETXh0THgarRqXrhb+ngKU+WGArOZ8njPi5T0b56I7xC8l9wc++TxDYBDeEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QR19jxLC; 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="QR19jxLC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2192E1F000E9; Tue, 21 Jul 2026 22:38:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784673519; bh=24GFmxEZ66lVtO5Y91Y7Pvm8sWrbAkOiZjSAbHxYaG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=QR19jxLCnB7NGBorm61013OZ1PeFJ3Mxbd3XEPxls07F2OIwSGvDmwp1wnnkyGPNG ZwpwJRC0EVqaurQdI2W1vOkFRc2PxBaNteBbJcwv+F08by6fxNywRagZPNQC9rh6be qo1BfweWsHm+0hA+UaoB7YTMWzDJm8B/Q8wtgQZE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, NeilBrown , Tejun Heo , "Rafael J. Wysocki (Intel)" , Danilo Krummrich , Sasha Levin Subject: [PATCH 5.10 193/699] sysfs: clamp show() return value in sysfs_kf_read() Date: Tue, 21 Jul 2026 17:19:12 +0200 Message-ID: <20260721152400.052508482@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152355.667394603@linuxfoundation.org> References: <20260721152355.667394603@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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Greg Kroah-Hartman [ Upstream commit 454257f6d124a92342dcbb7710c03dd6ef96c731 ] sysfs_kf_seq_show() defends against buggy show() callbacks that return larger than PAGE_SIZE by clamping the value and printing a warning. sysfs_kf_read(), the prealloc variant, has no such defense. The only current in-tree user of __ATTR_PREALLOC is drivers/md/md.c, whose show() callbacks are well-behaved, so this is hardening against future drivers doing foolish things and out-of-tree code doing even more foolish things. Cc: NeilBrown Cc: Tejun Heo Fixes: 2b75869bba67 ("sysfs/kernfs: allow attributes to request write buffer be pre-allocated.") Assisted-by: gregkh_clanker_t1000 Reviewed-by: Rafael J. Wysocki (Intel) Reviewed-by: Danilo Krummrich Link: https://patch.msgid.link/2026052000-drove-unicycle-d61b@gregkh Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- fs/sysfs/file.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index f51b2396830f4a..d3dd04d3997d2d 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -117,6 +117,10 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf, len = ops->show(kobj, of->kn->priv, buf); if (len < 0) return len; + if (len >= (ssize_t)PAGE_SIZE) { + printk("fill_read_buffer: %pS returned bad count\n", ops->show); + len = PAGE_SIZE - 1; + } if (pos) { if (len <= pos) return 0; -- 2.53.0