From: Seth Forshee <firstname.lastname@example.org> To: "Eric W. Biederman" <email@example.com> Cc: Linux Containers <firstname.lastname@example.org>, email@example.com, "Serge E. Hallyn" <firstname.lastname@example.org>, Christian Brauner <email@example.com>, firstname.lastname@example.org Subject: Re: [REVIEW][PATCH 2/6] vfs: Allow userns root to call mknod on owned filesystems. Date: Thu, 24 May 2018 12:22:32 -0500 [thread overview] Message-ID: <20180524172232.GS3401@ubuntu-xps13> (raw) In-Reply-To: <email@example.com> On Thu, May 24, 2018 at 11:55:45AM -0500, Eric W. Biederman wrote: > Seth Forshee <firstname.lastname@example.org> writes: > > > On Wed, May 23, 2018 at 06:25:34PM -0500, Eric W. Biederman wrote: > >> These filesystems already always set SB_I_NODEV so mknod will not be > >> useful for gaining control of any devices no matter their permissions. > >> This will allow overlayfs and applications to fakeroot to use device > >> nodes to represent things on disk. > >> > >> Signed-off-by: "Eric W. Biederman" <email@example.com> > > > > For a normal filesystem this does seem safe enough. > > > > However, I'd also like to see us allow unprivileged mounting for > > overlayfs, and there we need to worry about whether this would allow a > > mknod in an underlying filesystem which should not be allowed. That > > mknod will be subject to this same check in the underlying filesystem > > using the credentials of the user that mounted the overaly fs, which > > should be sufficient to ensure that the mknod is permitted. > > Sufficient to ensure the mknod is not permitted on the underlying > filesystem. I believe you mean. Right, or in other words with the relaxed capability check a user still could not use an overlayfs mount in a user namespace to mknod in a filesystem when that user couldn't otherwise mknod in that filesystem. Sorry if I wasn't clear. > > > Thus this looks okay to me. > > > > Acked-by: Seth Forshee <firstname.lastname@example.org> > > Eric >
next prev parent reply other threads:[~2018-05-24 17:22 UTC|newest] Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-23 23:22 [REVIEW][PATCH 0/6] Wrapping up the vfs support for unprivileged mounts Eric W. Biederman 2018-05-23 23:25 ` [REVIEW][PATCH 1/6] vfs: Don't allow changing the link count of an inode with an invalid uid or gid Eric W. Biederman 2018-05-24 12:58 ` Seth Forshee 2018-05-24 22:30 ` Christian Brauner 2018-05-23 23:25 ` [REVIEW][PATCH 2/6] vfs: Allow userns root to call mknod on owned filesystems Eric W. Biederman 2018-05-24 13:55 ` Seth Forshee 2018-05-24 16:55 ` Eric W. Biederman 2018-05-24 17:22 ` Seth Forshee [this message] 2018-05-24 19:12 ` Christian Brauner 2018-05-23 23:25 ` [REVIEW][PATCH 3/6] fs: Allow superblock owner to replace invalid owners of inodes Eric W. Biederman 2018-05-23 23:41 ` [REVIEW][PATCH v2 " Eric W. Biederman 2018-05-24 22:30 ` Christian Brauner 2018-05-23 23:25 ` [REVIEW][PATCH 4/6] fs: Allow superblock owner to access do_remount_sb() Eric W. Biederman 2018-05-24 15:58 ` Christian Brauner 2018-05-24 16:45 ` Eric W. Biederman 2018-05-24 17:28 ` Christian Brauner 2018-05-23 23:25 ` [REVIEW][PATCH 5/6] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Eric W. Biederman 2018-05-24 15:57 ` Christian Brauner 2018-05-23 23:25 ` [REVIEW][PATCH 6/6] fs: Allow CAP_SYS_ADMIN in s_user_ns to freeze and thaw filesystems Eric W. Biederman 2018-05-24 15:59 ` Christian Brauner 2018-05-24 21:46 ` [REVIEW][PATCH 0/6] Wrapping up the vfs support for unprivileged mounts Theodore Y. Ts'o 2018-05-24 23:23 ` Eric W. Biederman 2018-05-25 3:57 ` Dave Chinner 2018-05-25 4:06 ` Darrick J. Wong 2018-05-29 13:12 ` Eric W. Biederman 2018-05-29 22:17 ` Dave Chinner 2018-05-30 2:34 ` Eric W. Biederman 2018-05-30 4:34 ` Dave Chinner 2018-05-29 15:40 ` Dongsu Park
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