From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Dongsu Park <dongsu@kinvolk.io>
Cc: linux-kernel@vger.kernel.org,
containers@lists.linux-foundation.org,
Alban Crequy <alban@kinvolk.io>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Seth Forshee <seth.forshee@canonical.com>,
Sargun Dhillon <sargun@sargun.me>,
linux-fsdevel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Luis R. Rodriguez" <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH 03/11] fs: Allow superblock owner to change ownership of inodes
Date: Fri, 5 Jan 2018 20:24:07 +0100 [thread overview]
Message-ID: <20180105192407.GF22430@wotan.suse.de> (raw)
In-Reply-To: <ac3d34002d7690f6ca5928b57b7fc4d707104b04.1512041070.git.dongsu@kinvolk.io>
On Fri, Dec 22, 2017 at 03:32:27PM +0100, Dongsu Park wrote:
> diff --git a/fs/attr.c b/fs/attr.c
> index 12ffdb6f..bf8e94f3 100644
> --- a/fs/attr.c
> +++ b/fs/attr.c
> @@ -18,6 +18,30 @@
> #include <linux/evm.h>
> #include <linux/ima.h>
>
> +static bool chown_ok(const struct inode *inode, kuid_t uid)
> +{
> + if (uid_eq(current_fsuid(), inode->i_uid) &&
> + uid_eq(uid, inode->i_uid))
> + return true;
> + if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))
> + return true;
> + if (ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
> + return true;
> + return false;
> +}
> +
> +static bool chgrp_ok(const struct inode *inode, kgid_t gid)
> +{
> + if (uid_eq(current_fsuid(), inode->i_uid) &&
> + (in_group_p(gid) || gid_eq(gid, inode->i_gid)))
> + return true;
> + if (capable_wrt_inode_uidgid(inode, CAP_CHOWN))
> + return true;
> + if (ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
> + return true;
> + return false;
> +}
> +
> /**
> * setattr_prepare - check if attribute changes to a dentry are allowed
> * @dentry: dentry to check
> @@ -52,17 +76,11 @@ int setattr_prepare(struct dentry *dentry, struct iattr *attr)
> goto kill_priv;
>
> /* Make sure a caller can chown. */
> - if ((ia_valid & ATTR_UID) &&
> - (!uid_eq(current_fsuid(), inode->i_uid) ||
> - !uid_eq(attr->ia_uid, inode->i_uid)) &&
> - !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
> + if ((ia_valid & ATTR_UID) && !chown_ok(inode, attr->ia_uid))
> return -EPERM;
I think this patch would read much better and easier to review if it was
split up by first adding the helpers, and then extending them afterwards.
>
> /* Make sure caller can chgrp. */
> - if ((ia_valid & ATTR_GID) &&
> - (!uid_eq(current_fsuid(), inode->i_uid) ||
> - (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
> - !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
> + if ((ia_valid & ATTR_GID) && !chgrp_ok(inode, attr->ia_gid))
> return -EPERM;
>
> /* Make sure a caller can chmod. */
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 31934cb9..9d50ec92 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -665,10 +665,17 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr)
> {
> int error;
> struct inode *inode = d_inode(dentry);
> + struct user_namespace *s_user_ns;
>
> if (attr->ia_valid & ATTR_MODE)
> return -EPERM;
>
> + /* Don't let anyone mess with weird proc files */
> + s_user_ns = inode->i_sb->s_user_ns;
> + if (!kuid_has_mapping(s_user_ns, inode->i_uid) ||
> + !kgid_has_mapping(s_user_ns, inode->i_gid))
> + return -EPERM;
> +
> error = setattr_prepare(dentry, attr);
> if (error)
> return error;
Are we sure proc is the only special one? How was it observed first that this was
require for proc? Has anyone tried fuzzing by trying this op with a slew of other
filesystems on all files?
Luis
next prev parent reply other threads:[~2018-01-05 19:24 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 [this message]
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 ` [PATCH v7 7/7] fuse: Restrict allow_other to the superblock's namespace or a descendant Eric W. Biederman
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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