This is a note to let you know that I've just added the patch titled
mnt: Refactor the logic for mounting sysfs and proc in a user namespace
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mnt-refactor-the-logic-for-mounting-sysfs-and-proc-in-a-user-namespace.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1b852bceb0d111e510d1a15826ecc4a19358d512 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Date: Fri, 8 May 2015 23:22:29 -0500
Subject: mnt: Refactor the logic for mounting sysfs and proc in a user namespace
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
commit 1b852bceb0d111e510d1a15826ecc4a19358d512 upstream.
Fresh mounts of proc and sysfs are a very special case that works very
much like a bind mount. Unfortunately the current structure can not
preserve the MNT_LOCK... mount flags. Therefore refactor the logic
into a form that can be modified to preserve those lock bits.
Add a new filesystem flag FS_USERNS_VISIBLE that requires some mount
of the filesystem be fully visible in the current mount namespace,
before the filesystem may be mounted.
Move the logic for calling fs_fully_visible from proc and sysfs into
fs/namespace.c where it has greater access to mount namespace state.
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 8 +++++++-
fs/proc/root.c | 5 +----
fs/sysfs/mount.c | 5 +----
include/linux/fs.h | 2 +-
4 files changed, 10 insertions(+), 10 deletions(-)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2334,6 +2334,8 @@ unlock:
return err;
}
+static bool fs_fully_visible(struct file_system_type *fs_type);
+
/*
* create a new mount for userspace and request it to be added into the
* namespace's tree
@@ -2365,6 +2367,10 @@ static int do_new_mount(struct path *pat
flags |= MS_NODEV;
mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
}
+ if (type->fs_flags & FS_USERNS_VISIBLE) {
+ if (!fs_fully_visible(type))
+ return -EPERM;
+ }
}
mnt = vfs_kern_mount(type, flags, name, data);
@@ -3166,7 +3172,7 @@ bool current_chrooted(void)
return chrooted;
}
-bool fs_fully_visible(struct file_system_type *type)
+static bool fs_fully_visible(struct file_system_type *type)
{
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
struct mount *mnt;
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -112,9 +112,6 @@ static struct dentry *proc_mount(struct
ns = task_active_pid_ns(current);
options = data;
- 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);
@@ -159,7 +156,7 @@ static struct file_system_type proc_fs_t
.name = "proc",
.mount = proc_mount,
.kill_sb = proc_kill_sb,
- .fs_flags = FS_USERNS_MOUNT,
+ .fs_flags = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
};
void __init proc_root_init(void)
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -31,9 +31,6 @@ static struct dentry *sysfs_mount(struct
bool new_sb;
if (!(flags & MS_KERNMOUNT)) {
- if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
- return ERR_PTR(-EPERM);
-
if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
return ERR_PTR(-EPERM);
}
@@ -58,7 +55,7 @@ static struct file_system_type sysfs_fs_
.name = "sysfs",
.mount = sysfs_mount,
.kill_sb = sysfs_kill_sb,
- .fs_flags = FS_USERNS_MOUNT,
+ .fs_flags = FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
};
int __init sysfs_init(void)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1863,6 +1863,7 @@ struct file_system_type {
#define FS_HAS_SUBTYPE 4
#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */
#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */
+#define FS_USERNS_VISIBLE 32 /* FS must already be visible */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *);
@@ -1950,7 +1951,6 @@ extern int vfs_ustat(dev_t, struct kstat
extern int freeze_super(struct super_block *super);
extern int thaw_super(struct super_block *super);
extern bool our_mnt(struct vfsmount *mnt);
-extern bool fs_fully_visible(struct file_system_type *);
extern int current_umask(void);
Patches currently in stable-queue which might be from ebiederm@xxxxxxxxxxxx are
queue-4.0/sysfs-create-mountpoints-with-sysfs_create_mount_point.patch
queue-4.0/sysfs-add-support-for-permanently-empty-directories-to-serve-as-mount-points.patch
queue-4.0/mnt-update-fs_fully_visible-to-test-for-permanently-empty-directories.patch
queue-4.0/mnt-refactor-the-logic-for-mounting-sysfs-and-proc-in-a-user-namespace.patch
queue-4.0/mnt-modify-fs_fully_visible-to-deal-with-locked-ro-nodev-and-atime.patch
queue-4.0/fs-add-helper-functions-for-permanently-empty-directories.patch
queue-4.0/sysctl-allow-creating-permanently-empty-directories-that-serve-as-mountpoints.patch
queue-4.0/kernfs-add-support-for-always-empty-directories.patch
queue-4.0/proc-allow-creating-permanently-empty-directories-that-serve-as-mount-points.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html