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From: Christian Brauner <christian.brauner@ubuntu.com>
To: "Stéphane Graber" <stgraber@ubuntu.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Aleksa Sarai" <cyphar@cyphar.com>,
	"Jann Horn" <jannh@google.com>
Cc: smbarber@chromium.org, Seth Forshee <seth.forshee@canonical.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Serge Hallyn <serge@hallyn.com>, James Morris <jmorris@namei.org>,
	Kees Cook <keescook@chromium.org>,
	Jonathan Corbet <corbet@lwn.net>, Phil Estes <estesp@gmail.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	containers@lists.linux-foundation.org,
	linux-security-module@vger.kernel.org, linux-api@vger.kernel.org,
	Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH v2 10/28] sys:__sys_setgid(): handle fsid mappings
Date: Fri, 14 Feb 2020 19:35:36 +0100
Message-ID: <20200214183554.1133805-11-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20200214183554.1133805-1-christian.brauner@ubuntu.com>

Switch setgid() to lookup fsids in the fsid mappings. If no fsid mappings are
setup the behavior is unchanged, i.e. fsids are looked up in the id mappings.
The kfsid to cleanly handle userns visible filesystem is set as before.

We require that a user must have a valid fsid mapping for the target id. This
is consistent with how the setid calls work today without fsid mappings.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
- Christian Brauner <christian.brauner@ubuntu.com>:
  - set kfsid which is used when dealing with proc permission checking
---
 kernel/sys.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index a8eefd748327..aa379fb5e93b 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -416,24 +416,31 @@ long __sys_setgid(gid_t gid)
 	const struct cred *old;
 	struct cred *new;
 	int retval;
-	kgid_t kgid;
+	kgid_t kgid, kfsgid;
 
 	kgid = make_kgid(ns, gid);
 	if (!gid_valid(kgid))
 		return -EINVAL;
 
+	kfsgid = make_kfsgid(ns, gid);
+	if (!gid_valid(kfsgid))
+		return -EINVAL;
+
 	new = prepare_creds();
 	if (!new)
 		return -ENOMEM;
 	old = current_cred();
 
 	retval = -EPERM;
-	if (ns_capable(old->user_ns, CAP_SETGID))
-		new->gid = new->egid = new->sgid = new->fsgid = kgid;
-	else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid))
-		new->egid = new->fsgid = kgid;
-	else
+	if (ns_capable(old->user_ns, CAP_SETGID)) {
+		new->gid = new->egid = new->sgid = new->kfsgid = kgid;
+		new->fsgid = kfsgid;
+	} else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid)) {
+		new->egid = new->kfsgid = kgid;
+		new->fsgid = kfsgid;
+	} else {
 		goto error;
+	}
 
 	return commit_creds(new);
 
-- 
2.25.0


  parent reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 18:35 [PATCH v2 00/28] user_namespace: introduce " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 01/28] user_namespace: introduce fsid mappings infrastructure Christian Brauner
2020-02-14 18:35 ` [PATCH v2 02/28] proc: add /proc/<pid>/fsuid_map Christian Brauner
2020-02-14 18:35 ` [PATCH v2 03/28] proc: add /proc/<pid>/fsgid_map Christian Brauner
2020-02-14 18:35 ` [PATCH v2 04/28] fsuidgid: add fsid mapping helpers Christian Brauner
2020-02-14 19:11   ` Jann Horn
2020-02-16 16:55     ` Christian Brauner
2020-02-14 18:35 ` [PATCH v2 05/28] proc: task_state(): use from_kfs{g,u}id_munged Christian Brauner
2020-02-14 18:35 ` [PATCH v2 06/28] cred: add kfs{g,u}id Christian Brauner
2020-02-14 18:35 ` [PATCH v2 07/28] sys: __sys_setfsuid(): handle fsid mappings Christian Brauner
2020-02-14 18:35 ` [PATCH v2 08/28] sys: __sys_setfsgid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 09/28] sys:__sys_setuid(): " Christian Brauner
2020-02-14 18:35 ` Christian Brauner [this message]
2020-02-14 18:35 ` [PATCH v2 11/28] sys:__sys_setreuid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 12/28] sys:__sys_setregid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 13/28] sys:__sys_setresuid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 14/28] sys:__sys_setresgid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 15/28] fs: add is_userns_visible() helper Christian Brauner
2020-02-14 18:35 ` [PATCH v2 16/28] namei: may_{o_}create(): handle fsid mappings Christian Brauner
2020-02-14 18:35 ` [PATCH v2 17/28] inode: inode_owner_or_capable(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 18/28] capability: privileged_wrt_inode_uidgid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 19/28] stat: " Christian Brauner
2020-02-14 19:03   ` Tycho Andersen
2020-02-16 14:12     ` Christian Brauner
2020-02-14 18:35 ` [PATCH v2 20/28] open: " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 21/28] posix_acl: " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 22/28] attr: notify_change(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 23/28] commoncap: cap_bprm_set_creds(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 24/28] commoncap: cap_task_fix_setuid(): " Christian Brauner
2020-02-14 18:35 ` [PATCH v2 25/28] commoncap: handle fsid mappings with vfs caps Christian Brauner
2020-02-14 18:35 ` [PATCH v2 26/28] exec: bprm_fill_uid(): handle fsid mappings Christian Brauner
2020-02-14 18:35 ` [PATCH v2 27/28] ptrace: adapt ptrace_may_access() to always uses unmapped fsids Christian Brauner
2020-02-14 18:35 ` [PATCH v2 28/28] devpts: handle fsid mappings Christian Brauner
2020-02-16 15:55 ` [PATCH v2 00/28] user_namespace: introduce " Florian Weimer
2020-02-16 16:40   ` Christian Brauner
2020-02-17 21:06 ` James Bottomley
2020-02-17 21:20   ` Christian Brauner
2020-02-17 22:35     ` James Bottomley
2020-02-17 23:05       ` Christian Brauner
2020-02-17 21:11 ` James Bottomley
     [not found]   ` <CA+enf=vwd-dxzve87t7Mw1Z35RZqdLzVaKq=fZ4EGOpnES0f5w@mail.gmail.com>
2020-02-17 22:02     ` Stéphane Graber
2020-02-17 23:03     ` James Bottomley
2020-02-17 23:11       ` Stéphane Graber

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