Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EBC0C384CD5; Thu, 17 Sep 2026 18:52:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789671170; cv=none; b=ReEgW3QLCzAeycFPx2fVliMg9DGkR6Lk1Me+v/iGKiVfPwEs2XtA3RTcSXmIG5kZemHHSjfhjXHA26k3LKogUohkKEfiq0OYt/6RBxrQa3G1pRSX+S+7sRsFSMLM8tgHCQhRdZoBRHxijABRTLars5VjEbhilnGafsdoii9xKl4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789671170; c=relaxed/simple; bh=Fohb/I5CekG2qgPGY6CUjsJ4HVsVuTGcQ9f4watqCBY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AaWZdMnK8U28NiVAWehs/KmB86W7fFeZOrLVzbeX7cyXiY1RYaja9byLI5fmzaZxpC9XDhtU+UMj0p9TNez9QbFwzPD0kzcUsjfa0JQ3KNP9kJlKhcXi8G0BJp6m1h8DXCs3FniQ46+RmFQyuRTpufuHtTwwuEOVgeOZfOGICuc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f/QGnVQ/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f/QGnVQ/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A37B1F000FF; Thu, 17 Sep 2026 18:52:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789671168; bh=7cETDCskmfkezOPXcyYMgMcoFcHPb4K8a0Ut2ABl98w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=f/QGnVQ/mMoavafagPp7+tZo8EMOXmhDWOofzDQTaVZ9vMryAdpHF/WegL4aWyyO+ 9Rk2ti8Ye6BwUkglJyNi7AjEDyAOjkNUqilxHG12ypP2Gb7oG/LS24HmrBxXWqym+S X6o8ANFuJNkvHUGkvTrBZj23fmSdMAv3L3kfN+c4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, TencentOS Corvus AI , Aohan Mei , David Howells , Paulo Alcantara Subject: [PATCH 6.12 0889/1102] smb: client: reject userspace cifs.idmap descriptions Date: Thu, 17 Sep 2026 16:13:52 +0100 Message-ID: <20260917151602.897996464@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151539.408551884@linuxfoundation.org> References: <20260917151539.408551884@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aohan Mei commit d9d7eeb0cea5b55b82888f443622fd8d4ee064f3 upstream. cifs.idmap key descriptions carry authority-bearing fields (owner and group SIDs and uid/gid values in "os:"/"gs:"/"oi:"/"gi:" form) that the cifs.idmap upcall helper treats as kernel-originating inputs. Unlike its sibling cifs.spnego, the cifs.idmap key type has no vet_description hook, so userspace can create keys of this type through request_key(2)/add_key(2) and supply those fields without CIFS origin. A request_key(2) call with a non-NULL callout then drives a root usermodehelper upcall (/sbin/request-key -> cifs.idmap) that consumes the unvetted description in root context. Only accept cifs.idmap descriptions while CIFS is using its private root_cred to request the key. id_to_sid()/sid_to_id() already run under override_creds(root_cred), so the kernel-originated path is unaffected. This mirrors commit 3da1fdf4efbc ("smb: client: reject userspace cifs.spnego descriptions"), which applied the same restriction to cifs.spnego. Fixes: 4d79dba0e007 ("cifs: Add idmap key and related data structures and functions (try #17 repost)") Reported-by: TencentOS Corvus AI Cc: stable@vger.kernel.org Assisted-by: CodeBuddy:Kimi-K3 Signed-off-by: Aohan Mei Acked-by: David Howells Signed-off-by: Paulo Alcantara Signed-off-by: Greg Kroah-Hartman --- fs/smb/client/cifsacl.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) --- a/fs/smb/client/cifsacl.c +++ b/fs/smb/client/cifsacl.c @@ -101,8 +101,23 @@ cifs_idmap_key_destroy(struct key *key) kfree(key->payload.data[0]); } +static int +cifs_idmap_key_vet_description(const char *description) +{ + /* + * cifs.idmap descriptions are authority-bearing inputs to the + * cifs.idmap upcall helper. Only allow the kernel to create this + * type of key using the private root_cred installed in + * init_cifs_idmap; reject userspace request_key(2)/add_key(2). + */ + if (current_cred() != root_cred) + return -EPERM; + return 0; +} + static struct key_type cifs_idmap_key_type = { .name = "cifs.idmap", + .vet_description = cifs_idmap_key_vet_description, .instantiate = cifs_idmap_key_instantiate, .destroy = cifs_idmap_key_destroy, .describe = user_describe,