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From: "Eric W. Biederman" <ebiederm@xmission.com>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	containers@lists.linux-foundation.org,
	linux-fsdevel@vger.kernel.org, Alban Crequy <alban@kinvolk.io>,
	Seth Forshee <seth.forshee@canonical.com>,
	Sargun Dhillon <sargun@sargun.me>,
	Dongsu Park <dongsu@kinvolk.io>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>
Subject: [PATCH v7 7/7] fuse: Restrict allow_other to the superblock's namespace or a descendant
Date: Mon, 26 Feb 2018 17:53:02 -0600	[thread overview]
Message-ID: <20180226235302.12708-7-ebiederm@xmission.com> (raw)
In-Reply-To: <87po4rz4ui.fsf_-_@xmission.com>

From: Seth Forshee <seth.forshee@canonical.com>

Unprivileged users are normally restricted from mounting with the
allow_other option by system policy, but this could be bypassed
for a mount done with user namespace root permissions. In such
cases allow_other should not allow users outside the userns
to access the mount as doing so would give the unprivileged user
the ability to manipulate processes it would otherwise be unable
to manipulate. Restrict allow_other to apply to users in the same
userns used at mount or a descendant of that namespace. Also
export current_in_userns() for use by fuse when built as a
module.

Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Dongsu Park <dongsu@kinvolk.io>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 fs/fuse/dir.c           | 2 +-
 kernel/user_namespace.c | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 79cca1687457..0cbd1ff3dd48 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1030,7 +1030,7 @@ int fuse_allow_current_process(struct fuse_conn *fc)
 	const struct cred *cred;
 
 	if (fc->allow_other)
-		return 1;
+		return current_in_userns(fc->user_ns);
 
 	cred = current_cred();
 	if (uid_eq(cred->euid, fc->user_id) &&
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 246d4d4ce5c7..492c255e6c5a 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -1235,6 +1235,7 @@ bool current_in_userns(const struct user_namespace *target_ns)
 {
 	return in_userns(target_ns, current_user_ns());
 }
+EXPORT_SYMBOL(current_in_userns);
 
 static inline struct user_namespace *to_user_ns(struct ns_common *ns)
 {
-- 
2.14.1

  parent reply	other threads:[~2018-02-26 23:54 UTC|newest]

Thread overview: 107+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-22 14:32 [PATCH v5 00/11] FUSE mounts from non-init user namespaces Dongsu Park
2017-12-22 14:32 ` [PATCH 01/11] block_dev: Support checking inode permissions in lookup_bdev() Dongsu Park
2017-12-22 18:59   ` Coly Li
2017-12-23 12:00     ` Dongsu Park
2017-12-23  3:03   ` Serge E. Hallyn
2017-12-22 14:32 ` [PATCH 02/11] mtd: Check permissions towards mtd block device inode when mounting Dongsu Park
2017-12-22 21:06   ` Richard Weinberger
2017-12-23 12:18     ` Dongsu Park
2017-12-23 12:56       ` Richard Weinberger
2017-12-23  3:05   ` Serge E. Hallyn
2017-12-22 14:32 ` [PATCH 03/11] fs: Allow superblock owner to change ownership of inodes Dongsu Park
2017-12-23  3:17   ` Serge E. Hallyn
2018-01-05 19:24   ` Luis R. Rodriguez
2018-01-09 15:10     ` Dongsu Park
2018-01-09 17:23       ` Luis R. Rodriguez
2018-02-13 13:18   ` Miklos Szeredi
2018-02-16 22:00     ` Eric W. Biederman
2017-12-22 14:32 ` [PATCH 04/11] fs: Don't remove suid for CAP_FSETID for userns root Dongsu Park
2017-12-23  3:26   ` Serge E. Hallyn
2017-12-23 12:38     ` Dongsu Park
2018-02-13 13:37       ` Miklos Szeredi
2017-12-22 14:32 ` [PATCH 05/11] fs: Allow superblock owner to access do_remount_sb() Dongsu Park
2017-12-23  3:30   ` Serge E. Hallyn
2017-12-22 14:32 ` [PATCH 06/11] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Dongsu Park
2017-12-23  3:33   ` Serge E. Hallyn
2017-12-22 14:32 ` [PATCH 07/11] fs: Allow CAP_SYS_ADMIN in s_user_ns to freeze and thaw filesystems Dongsu Park
2017-12-23  3:39   ` Serge E. Hallyn
2018-02-14 12:28   ` Miklos Szeredi
2018-02-19 22:56     ` Eric W. Biederman
2017-12-22 14:32 ` [PATCH 08/11] fuse: Support fuse filesystems outside of init_user_ns Dongsu Park
2017-12-23  3:46   ` Serge E. Hallyn
2018-01-17 10:59   ` Alban Crequy
2018-01-17 14:29     ` Seth Forshee
2018-01-17 18:56       ` Alban Crequy
2018-01-17 19:31         ` Seth Forshee
2018-01-18 10:29           ` Alban Crequy
2018-02-12 15:57   ` Miklos Szeredi
2018-02-12 16:35     ` Eric W. Biederman
2018-02-13 10:20       ` Miklos Szeredi
2018-02-16 21:52         ` Eric W. Biederman
2018-02-20  2:12   ` Eric W. Biederman
2017-12-22 14:32 ` [PATCH 09/11] fuse: Restrict allow_other to the superblock's namespace or a descendant Dongsu Park
2017-12-23  3:50   ` Serge E. Hallyn
2018-02-19 23:16   ` Eric W. Biederman
2017-12-22 14:32 ` [PATCH 10/11] fuse: Allow user namespace mounts Dongsu Park
2017-12-23  3:51   ` Serge E. Hallyn
2018-02-14 13:44   ` Miklos Szeredi
2018-02-15  8:46     ` Miklos Szeredi
2017-12-22 14:32 ` [PATCH 11/11] evm: Don't update hmacs in user ns mounts Dongsu Park
2017-12-23  4:03   ` Serge E. Hallyn
2017-12-24  5:12     ` Mimi Zohar
2017-12-24  5:56       ` Mimi Zohar
2017-12-25  7:05 ` [PATCH v5 00/11] FUSE mounts from non-init user namespaces Eric W. Biederman
2018-01-09 15:05   ` Dongsu Park
2018-01-18 14:58     ` Alban Crequy
2018-02-19 23:09       ` Eric W. Biederman
2018-02-13 11:32 ` Miklos Szeredi
2018-02-16 21:53   ` Eric W. Biederman
2018-02-21 20:24 ` [PATCH v6 0/6] fuse: " Eric W. Biederman
2018-02-21 20:29   ` [PATCH v6 1/5] fuse: Remove the buggy retranslation of pids in fuse_dev_do_read Eric W. Biederman
2018-02-22 10:13     ` Miklos Szeredi
2018-02-22 19:04       ` Eric W. Biederman
2018-02-21 20:29   ` [PATCH v6 2/5] fuse: Fail all requests with invalid uids or gids Eric W. Biederman
2018-02-22 10:26     ` Miklos Szeredi
2018-02-22 18:15       ` Eric W. Biederman
2018-02-21 20:29   ` [PATCH v6 3/5] fuse: Support fuse filesystems outside of init_user_ns Eric W. Biederman
2018-02-21 20:29   ` [PATCH v6 4/5] fuse: Ensure posix acls are translated " Eric W. Biederman
2018-02-22 11:40     ` Miklos Szeredi
2018-02-22 19:18       ` Eric W. Biederman
2018-02-22 22:50         ` Eric W. Biederman
2018-02-26  7:47           ` Miklos Szeredi
2018-02-26 16:35             ` Eric W. Biederman
2018-02-26 21:51               ` Eric W. Biederman
2018-02-21 20:29   ` [PATCH v6 5/5] fuse: Restrict allow_other to the superblock's namespace or a descendant Eric W. Biederman
2018-02-26 23:52   ` [PATCH v7 0/7] fuse: mounts from non-init user namespaces Eric W. Biederman
2018-02-26 23:52     ` [PATCH v7 1/7] fuse: Remove the buggy retranslation of pids in fuse_dev_do_read Eric W. Biederman
2018-02-26 23:52     ` [PATCH v7 2/7] fuse: Fail all requests with invalid uids or gids Eric W. Biederman
2018-02-26 23:52     ` [PATCH v7 3/7] fs/posix_acl: Document that get_acl respects ACL_DONT_CACHE Eric W. Biederman
2018-02-27  1:13       ` Linus Torvalds
2018-02-27  2:53         ` Eric W. Biederman
2018-02-27  3:14           ` Eric W. Biederman
2018-02-27  3:41             ` Linus Torvalds
2018-03-02 19:53               ` [RFC][PATCH] fs/posix_acl: Update the comments and support lightweight cache skipping Eric W. Biederman
2018-02-27  3:36           ` [PATCH v7 3/7] fs/posix_acl: Document that get_acl respects ACL_DONT_CACHE Linus Torvalds
2018-02-26 23:52     ` [PATCH v7 4/7] fuse: Cache a NULL acl when FUSE_GETXATTR returns -ENOSYS Eric W. Biederman
2018-02-26 23:53     ` [PATCH v7 5/7] fuse: Simplfiy the posix acl handling logic Eric W. Biederman
2018-02-27  9:00       ` Miklos Szeredi
2018-03-02 21:49         ` Eric W. Biederman
2018-02-26 23:53     ` [PATCH v7 6/7] fuse: Support fuse filesystems outside of init_user_ns Eric W. Biederman
2018-02-26 23:53     ` Eric W. Biederman [this message]
2018-03-02 21:58     ` [PATCH v8 0/6] fuse: mounts from non-init user namespaces Eric W. Biederman
2018-03-02 21:59       ` [PATCH v8 1/6] fs/posix_acl: Update the comments and support lightweight cache skipping Eric W. Biederman
2018-03-05  9:53         ` Miklos Szeredi
2018-03-05 13:53           ` Eric W. Biederman
2018-03-02 21:59       ` [PATCH v8 2/6] fuse: Simplfiy the posix acl handling logic Eric W. Biederman
2018-03-02 21:59       ` [PATCH v8 3/6] fuse: Remove the buggy retranslation of pids in fuse_dev_do_read Eric W. Biederman
2018-03-02 21:59       ` [PATCH v8 4/6] fuse: Fail all requests with invalid uids or gids Eric W. Biederman
2018-03-02 21:59       ` [PATCH v8 5/6] fuse: Support fuse filesystems outside of init_user_ns Eric W. Biederman
2018-03-02 21:59       ` [PATCH v8 6/6] fuse: Restrict allow_other to the superblock's namespace or a descendant Eric W. Biederman
2018-03-08 21:23       ` [PATCH v9 0/4] fuse: mounts from non-init user namespaces Eric W. Biederman
2018-03-08 21:24         ` [PATCH v9 1/4] fuse: Remove the buggy retranslation of pids in fuse_dev_do_read Eric W. Biederman
2018-03-08 21:24         ` [PATCH v9 2/4] fuse: Fail all requests with invalid uids or gids Eric W. Biederman
2018-03-08 21:24         ` [PATCH v9 3/4] fuse: Support fuse filesystems outside of init_user_ns Eric W. Biederman
2018-03-08 21:24         ` [PATCH v9 4/4] fuse: Restrict allow_other to the superblock's namespace or a descendant Eric W. Biederman
2018-03-20 16:25         ` [PATCH v9 0/4] fuse: mounts from non-init user namespaces Miklos Szeredi
2018-03-20 18:27           ` Eric W. Biederman
2018-03-21  8:38             ` Miklos Szeredi

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