From aee1c13dd0f6c2fc56e0e492b349ee8ac655880f Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Mon, 25 Mar 2013 19:57:10 -0700 Subject: proc: Restrict mounting the proc filesystem Don't allow mounting the proc filesystem unless the caller has CAP_SYS_ADMIN rights over the pid namespace. The principle here is if you create or have capabilities over it you can mount it, otherwise you get to live with what other people have mounted. Andy pointed out that this is needed to prevent users in a user namespace from remounting proc and specifying different hidepid and gid options on already existing proc mounts. Cc: stable@vger.kernel.org Reported-by: Andy Lutomirski Signed-off-by: "Eric W. Biederman" --- fs/proc/root.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs/proc/root.c') diff --git a/fs/proc/root.c b/fs/proc/root.c index 229e366598da..38bd5d423fcd 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -110,7 +110,8 @@ static struct dentry *proc_mount(struct file_system_type *fs_type, ns = task_active_pid_ns(current); options = data; - if (!current_user_ns()->may_mount_proc) + if (!current_user_ns()->may_mount_proc || + !ns_capable(ns->user_ns, CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); } -- cgit v1.2.3 From e51db73532955dc5eaba4235e62b74b460709d5b Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sat, 30 Mar 2013 19:57:41 -0700 Subject: userns: Better restrictions on when proc and sysfs can be mounted Rely on the fact that another flavor of the filesystem is already mounted and do not rely on state in the user namespace. Verify that the mounted filesystem is not covered in any significant way. I would love to verify that the previously mounted filesystem has no mounts on top but there are at least the directories /proc/sys/fs/binfmt_misc and /sys/fs/cgroup/ that exist explicitly for other filesystems to mount on top of. Refactor the test into a function named fs_fully_visible and call that function from the mount routines of proc and sysfs. This makes this test local to the filesystems involved and the results current of when the mounts take place, removing a weird threading of the user namespace, the mount namespace and the filesystems themselves. Signed-off-by: "Eric W. Biederman" --- fs/proc/root.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'fs/proc/root.c') diff --git a/fs/proc/root.c b/fs/proc/root.c index 38bd5d423fcd..45e5fb7da09b 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -110,8 +110,11 @@ static struct dentry *proc_mount(struct file_system_type *fs_type, ns = task_active_pid_ns(current); options = data; - if (!current_user_ns()->may_mount_proc || - !ns_capable(ns->user_ns, CAP_SYS_ADMIN)) + if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type)) + return ERR_PTR(-EPERM); + + /* Does the mounter have privilege over the pid namespace? */ + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); } -- cgit v1.2.3