From patchwork Sun Mar 2 16:06:39 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Christian_G=C3=B6ttsche?= X-Patchwork-Id: 13997875 Received: from server02.seltendoof.de (server02.seltendoof.de [168.119.48.163]) (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 084AF1E3761; Sun, 2 Mar 2025 16:07:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=168.119.48.163 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740931628; cv=none; b=tX7btjRylkYHryrA+Ejyp8zo6WdZwwxamCP6/iIqVnsrFuEVDJVtHUfutqHE80tG+L5zFkt+1xvpDLeQIFuUMhORI+opBvgmu9crTStYsqONzvktAOlvt8dLUWMLbko27nDQzSZoJkKdOHGOyj8SA9g5vhs7Lblmpi8QmY1NM+g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740931628; c=relaxed/simple; bh=DwoObYbkc3t6mMKbabMcq7AMLtAfZbBxFbz7lxK4ZC8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=F0X1s326fOv402WmZZ+Ta8A0sGCVEhCp3KPohGLIHcLKw+HaYSWMSbw8GCs0I0yW5su1GD4WXHYiEx6ne1BD5mmadoTFPhjv60HRDmRz6vD55yZiOMjBkcuoIa9uH8l7Dx5p7s/lWlL/7AIbgJrepd+ZMSInPxy831cIpGfxSZc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=seltendoof.de; spf=pass smtp.mailfrom=seltendoof.de; dkim=pass (2048-bit key) header.d=seltendoof.de header.i=@seltendoof.de header.b=rW723r6b; arc=none smtp.client-ip=168.119.48.163 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=seltendoof.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=seltendoof.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=seltendoof.de header.i=@seltendoof.de header.b="rW723r6b" From: =?utf-8?q?Christian_G=C3=B6ttsche?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=seltendoof.de; s=2023072701; t=1740931624; h=from:from:reply-to: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=LtVFyKPYvAG6nPAlnlSRsIED7/Fit5RjlOi+m21VZYs=; b=rW723r6bWSv6qn26AEbrStX87CkVu9G/7vNGrh7xh7Lqn7pp5kWJbhTClYidy6wk+Y+7sd FjPR7nS2CFldQESu5vxVqQRKbzDULfHYgaqGYBjNrElC8Jp/+8E5Ctfj1Nv59jeyJqvS98 yhpZrwB0FKmtPiiVuoqWjkBdcS/5eOoj5FPfR9gm5C7XWNjjza4nuEYR9IxTQ0lpuWjwCZ e+OlRPH2PFwomxohnhpClrlM995TmC9Xbrwm+7wdfa0h0OYtxXTqP8FO7MHjgM164WRD/j 93uAuVblah5062CFYFw/SQT9UgQc9mpRBtCUpTLTwBR1k7kbipwv85mDQlL9vg== To: Cc: =?utf-8?q?Christian_G=C3=B6ttsche?= , Serge Hallyn , Jan Kara , Julia Lawall , Nicolas Palix , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, cocci@inria.fr, "Theodore Ts'o" , Andreas Dilger , linux-ext4@vger.kernel.org Subject: [PATCH v2 03/11] ext4: reorder capability check last Date: Sun, 2 Mar 2025 17:06:39 +0100 Message-ID: <20250302160657.127253-2-cgoettsche@seltendoof.de> In-Reply-To: <20250302160657.127253-1-cgoettsche@seltendoof.de> References: <20250302160657.127253-1-cgoettsche@seltendoof.de> Reply-To: cgzones@googlemail.com Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Christian Göttsche capable() calls refer to enabled LSMs whether to permit or deny the request. This is relevant in connection with SELinux, where a capability check results in a policy decision and by default a denial message on insufficient permission is issued. It can lead to three undesired cases: 1. A denial message is generated, even in case the operation was an unprivileged one and thus the syscall succeeded, creating noise. 2. To avoid the noise from 1. the policy writer adds a rule to ignore those denial messages, hiding future syscalls, where the task performs an actual privileged operation, leading to hidden limited functionality of that task. 3. To avoid the noise from 1. the policy writer adds a rule to permit the task the requested capability, while it does not need it, violating the principle of least privilege. Signed-off-by: Christian Göttsche Reviewed-by: Serge Hallyn --- fs/ext4/balloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 8042ad873808..c48fd36b2d74 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -649,8 +649,8 @@ static int ext4_has_free_clusters(struct ext4_sb_info *sbi, /* Hm, nope. Are (enough) root reserved clusters available? */ if (uid_eq(sbi->s_resuid, current_fsuid()) || (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) || - capable(CAP_SYS_RESOURCE) || - (flags & EXT4_MB_USE_ROOT_BLOCKS)) { + (flags & EXT4_MB_USE_ROOT_BLOCKS) || + capable(CAP_SYS_RESOURCE)) { if (free_clusters >= (nclusters + dirty_clusters + resv_clusters))