From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8762C4F1FF; Sun, 28 Jan 2024 16:16:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706458575; cv=none; b=nZPAVvb9GCzbu+OYcGGnxf8aVhk/a9TgnBL+vRJy2iegGSM4sW1Ag75fLJ41fHjB6PevwhboNzUrpnULCOBYkqYQHZaloGcErhK0hBN1thlOwLP/5D/ZH6E9fE9CYt3D9QFG7dJdFXH5eU/yv47uPHFNaIhFBBVuhjJY2HgifbM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706458575; c=relaxed/simple; bh=bRb2TgQA90tQ63dWvVFph0qMSAhZizRyeXQGobEQo5U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gcW7kciQYzQnOhBMJCaPbJTK32P56AX5cHnrdPnCi8QzeY547TAffX62PBAgpM4MPsog/t3mI0HG875T/lN8Xu2eshZCL42wmzSIdHXkyTYX84pbjOfCRYxDGizYmx9e96tq8HxCi6/Yq+FKMDAERvHMdDC5kHiqvGfg3Zllq/U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YgkwXj0D; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YgkwXj0D" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8202C433B1; Sun, 28 Jan 2024 16:16:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706458575; bh=bRb2TgQA90tQ63dWvVFph0qMSAhZizRyeXQGobEQo5U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YgkwXj0DcTeiuiC6KL5/MXDaCIzb1+3BOlLSiOEzFqGssnCO+SgTBt6vPkCwO+IYB 2w4bjVCoUEn5wDFbDWZfpY+UyvUYBRfb/zM/aSZsZfeynWv9dJsMQzDeVBg8+pZmVD VjnGtO1na9mwXeqz8xefbyFMX4UTTYYz9XDKIpCVisbSZr96S/BdsLGYejqI/cLjiB dVB/28AieTKDxXafdVfq8pgT1Yglx4JwCKvdKy+60mrWROSeCcKoGOtnS8GCTFsVB9 ej0fUm3HchnkYV/Ea9OKp2Z+2V9mxgXHAWPoC7DDXax+41ZNjMTrj6nvsuqRTrVSrv xAxieQ2TbAcwg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Max Kellermann , Tejun Heo , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 5.10 05/13] fs/kernfs/dir: obey S_ISGID Date: Sun, 28 Jan 2024 11:15:51 -0500 Message-ID: <20240128161606.205221-5-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240128161606.205221-1-sashal@kernel.org> References: <20240128161606.205221-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.10.209 Content-Transfer-Encoding: 8bit From: Max Kellermann [ Upstream commit 5133bee62f0ea5d4c316d503cc0040cac5637601 ] Handling of S_ISGID is usually done by inode_init_owner() in all other filesystems, but kernfs doesn't use that function. In kernfs, struct kernfs_node is the primary data structure, and struct inode is only created from it on demand. Therefore, inode_init_owner() can't be used and we need to imitate its behavior. S_ISGID support is useful for the cgroup filesystem; it allows subtrees managed by an unprivileged process to retain a certain owner gid, which then enables sharing access to the subtree with another unprivileged process. -- v1 -> v2: minor coding style fix (comment) Signed-off-by: Max Kellermann Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20231208093310.297233-2-max.kellermann@ionos.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- fs/kernfs/dir.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index c91ee05cce74..0ba056e06e48 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -696,6 +696,18 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent, { struct kernfs_node *kn; + if (parent->mode & S_ISGID) { + /* this code block imitates inode_init_owner() for + * kernfs + */ + + if (parent->iattr) + gid = parent->iattr->ia_gid; + + if (flags & KERNFS_DIR) + mode |= S_ISGID; + } + kn = __kernfs_new_node(kernfs_root(parent), parent, name, mode, uid, gid, flags); if (kn) { -- 2.43.0