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 3FF3912CD93; Sun, 28 Jan 2024 16:15:38 +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=1706458538; cv=none; b=ZMuWaVMAYpYur9F1OAyKvYzySdvbcqdvaPGQ4ucXZS2AVvkpv5Cz/HfYT6PFQzyAp37UThKD6CcAqumq+GackLhMg/UWwPVYuddDzpp2w1MhWbyb1c8Gr9obltH7IspxZpgfrBX8UKEDu8l1HtpiG6LryaNSSJLiO6hoZwH5zxI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706458538; c=relaxed/simple; bh=+h8UwIgo2JSvj9tCrTavYxJpiKhEB2zmGZO2EJqh8zE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lJA4HCa9CRyiGhtLxlJVKqegDY73hzP9koXYsZfTEiEVVOg6OTLmp9xOi/eNNPuMADToBbzyN+wli1RV2UPkMmpUAQpVFgQ+jwchJ8BtwU38QFm1oY4vYvNHtrrH+t6Zz2C/Fq9NnpPaAEfShJmcqOoUwSsn6naYS+zLAqA0FdA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GmTNlocl; 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="GmTNlocl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64F1BC433C7; Sun, 28 Jan 2024 16:15:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706458538; bh=+h8UwIgo2JSvj9tCrTavYxJpiKhEB2zmGZO2EJqh8zE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GmTNloclwREBjKfnxjekxaWp3hudfeDvd9fcisp4oneUu0ReHN8pI0KksUBq6/8m0 OqhTkw1JL3eKS7SpnX39vaxJda79QUC8Px7kdXtApWTIrlHWqfPAxfqGjCisbbnm6C AswKQQ/C5ltagPnVqu/H7TUtTmqOGixNH2tt7JhL3kckt+36A24xpTwT5saC2Dblj9 FifCBQVDXiKMY5WTOkDKudhZIL3L9m67efGDCcQrd+z8EsS/4xGM9d+pNnzFFdZyBW QM86R4FC5Lb9b4+4bnvjyYAEucv5w1PxPX1WNq5/2dg0Xsa9OKFG8DPPqbydUYNP2W epOPYPeRcBYGA== 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 5.15 08/19] fs/kernfs/dir: obey S_ISGID Date: Sun, 28 Jan 2024 11:15:05 -0500 Message-ID: <20240128161524.204182-8-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240128161524.204182-1-sashal@kernel.org> References: <20240128161524.204182-1-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 5.15.148 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 6a1cb2a182b6..36430bdf9381 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -654,6 +654,18 @@ 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