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 C8223144629; Sun, 28 Jan 2024 16:16:45 +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=1706458605; cv=none; b=OBVSmZAESvcqo17QbCLFRpdJxnYa/ZbcNis93Bz3Z6r5VKP9lNJfjyHJkQ21yQOK9x4bs++iydHUNLw83Hb00J4rhbtpcbHHUFAllj+ncFp1hHYI4tpqCCPUF24OK0z7CFYoc9HfGoh2CkMaCvd/Fl7/xOqYSQxzB36g4Yl96E0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706458605; c=relaxed/simple; bh=TVrjnz4N4BXeetl0qonNX9Rk4p9IAvClyH7GaIBkBKA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mtxNCzMz0W10t8N74at3nfILYUmpY6+apgyf0xM/yLFFBbRokioLPQkjFZx8TN38Ir4MStPltatiXZFOa3tN+TR8OIf3dF/0KYN1Vbwk/hzbHprRDzvARvzoP+q2NRzzeed7Wcw8Nzl8vj4zGsLXhicY6TCK0qDo3GKOIewFw1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b+VxVNV7; 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="b+VxVNV7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88338C433F1; Sun, 28 Jan 2024 16:16:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706458605; bh=TVrjnz4N4BXeetl0qonNX9Rk4p9IAvClyH7GaIBkBKA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b+VxVNV77WSuGMXas77mF8GxZfpAViFVdLsarG2B9MbN9XoUgSBIa++gXGelx7aN1 8QDxiZe7xfAiGfytHCBLKFRoWzzU1chgP/+97GefEXBOeNEJwLxP9FGqsxUkWE+ew9 +2gdSS0FIQ7WAFnvyT7V8nTxeUq0SRSt/bkIjF2Vg1VnXStMzuqQEsqU9mEk7gqYRH ToXusGW3yZNbU8cGncStIq61ZqxPKSMwfK58rPBa/6SCCeUENBz1LmQRWrVra+VcwE OSG08/+zIHsASF/2cSRRPdkTW2nS6d57Fqo2Q9PcGvEHhJBu5wRHr3Df9G95xSa7YA DqFwVv4HgZkkA== 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 5.4 04/11] fs/kernfs/dir: obey S_ISGID Date: Sun, 28 Jan 2024 11:16:25 -0500 Message-ID: <20240128161637.205509-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240128161637.205509-1-sashal@kernel.org> References: <20240128161637.205509-1-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 5.4.268 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 d2068566c0b8..d3a602ea795b 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -702,6 +702,18 @@ 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