From nobody Sun Oct 5 10:47:04 2025 Received: from mout-p-201.mailbox.org (mout-p-201.mailbox.org [80.241.56.171]) (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 B6078206F23; Wed, 6 Aug 2025 06:07:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754460456; cv=none; b=enlnE6572VGgoP26qDdnn9MM48dbxKnnvTsthHlOjxPlWuafbPlJ8293KHiPe62qRH/CDKghN1ZKpiOVv24eisKH4YbB8KJQZcWYcAR4NpSAxfKsnT7kcSVmqSN/qMuSosjnFLYzgdreHr0DdwsWiM4LSgh86+xrHIZDdtVcU78= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754460456; c=relaxed/simple; bh=Ye39SgM+Etl8XRmkHnnUx23tWQlJ53yx1MHZm4Nu7EE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=A4MwbGZ1GggTo0BYD+Wj2qDj7OU1s018fDXJe167cXWqziW9pdlrdEsMUCGoK8WxG2pqJv6PAjioRMrLKELQ4AlljlKttdtvCtEBAdCE993pf8F5SnfKD4jiQ9a4yRazsxyYOgVDCggHX8Vn3EsBmVYLnreZ4gLgEE5ctVezgMc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com; spf=pass smtp.mailfrom=cyphar.com; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b=d6nyFjaN; arc=none smtp.client-ip=80.241.56.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cyphar.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cyphar.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cyphar.com header.i=@cyphar.com header.b="d6nyFjaN" Received: from smtp102.mailbox.org (smtp102.mailbox.org [10.196.197.102]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-201.mailbox.org (Postfix) with ESMTPS id 4bxfvw6fHPz9tLZ; Wed, 6 Aug 2025 08:07:24 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cyphar.com; s=MBO0001; t=1754460445; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hvjO1yXplYoS1k6lhx55wXs3NDrmm2HWfvZNqZWFq4s=; b=d6nyFjaNUaChikrH0suD1BoCbuUJMFnx+GFSOkZsOjxZKvHX8j0IvtXg8KbpKn5Qk1AYfQ LV97FsBEOhSjJrFCPB7NGoBhyME6wS6GVYXwlOwzPClPa8n7owq/eC6rkGmSPsNrXrlZ/B noBvX7L7GbdxO5A/Priyb2mWuZ8gNii6AyGKEG5CHmJ5obR3m33N7VTVPZcYPbrt4SMvRx kRvqB7lgDZTHrLZ7VBbtC5ePF3Jg+3999P4BRR5EcTXr9mtQxWpymgevAzRhb+DVexIXlp Mqzv9wIeatYWOcdaKE0uhgyHPml8tmTcjtKFOiCIHzuqTpjWGRBCfomBwCvn5w== From: Aleksa Sarai Date: Wed, 06 Aug 2025 16:07:06 +1000 Subject: [PATCH v2 2/2] vfs: output mount_too_revealing() errors to fscontext Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250806-errorfc-mount-too-revealing-v2-2-534b9b4d45bb@cyphar.com> References: <20250806-errorfc-mount-too-revealing-v2-0-534b9b4d45bb@cyphar.com> In-Reply-To: <20250806-errorfc-mount-too-revealing-v2-0-534b9b4d45bb@cyphar.com> To: Alexander Viro , Christian Brauner , Jan Kara Cc: David Howells , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Aleksa Sarai X-Developer-Signature: v=1; a=openpgp-sha256; l=1639; i=cyphar@cyphar.com; h=from:subject:message-id; bh=Ye39SgM+Etl8XRmkHnnUx23tWQlJ53yx1MHZm4Nu7EE=; b=owGbwMvMwCWmMf3Xpe0vXfIZT6slMWRM+shvsOc0v/rih8LTqlIP9V9Xt/ntUFQw44n2kZWHm janqb/N7ChlYRDjYpAVU2TZ5ucZumn+4ivJn1aywcxhZQIZwsDFKQAT+aXI8D/D+eTJf52CyvOc 11y/f1bNqcSDg+WYZZ3EgoAIpg1v0h0Z/vv4J8+ddHLaP4767nu5tX+SJpzRcFJz5//TXWguVyH ZwAIA X-Developer-Key: i=cyphar@cyphar.com; a=openpgp; fpr=C9C370B246B09F6DBCFC744C34401015D1D2D386 It makes little sense for fsmount() to output the warning message when mount_too_revealing() is violated to kmsg. Instead, the warning should be output (with a "VFS" prefix) to the fscontext log. In addition, include the same log message for mount_too_revealing() when doing a regular mount for consistency. With the newest fsopen()-based mount(8) from util-linux, the error messages now look like # mount -t proc proc /tmp mount: /tmp: fsmount() failed: VFS: Mount too revealing. dmesg(1) may have more information after failed mount system call. which could finally result in mount_too_revealing() errors being easier for users to detect and understand. Signed-off-by: Aleksa Sarai --- fs/namespace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 55f28cebbe7d..1e1c2c257e2e 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3820,8 +3820,10 @@ static int do_new_mount_fc(struct fs_context *fc, st= ruct path *mountpoint, int error; =20 error =3D security_sb_kern_mount(sb); - if (!error && mount_too_revealing(sb, &mnt_flags)) + if (!error && mount_too_revealing(sb, &mnt_flags)) { + errorfcp(fc, "VFS", "Mount too revealing"); error =3D -EPERM; + } =20 if (unlikely(error)) { fc_drop_locked(fc); @@ -4547,7 +4549,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, fl= ags, =20 ret =3D -EPERM; if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { - pr_warn("VFS: Mount too revealing\n"); + errorfcp(fc, "VFS", "Mount too revealing"); goto err_unlock; } =20 --=20 2.50.1