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mnt: Refactor the logic for mounting sysfs and proc in a user namespace

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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.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman
2015-05-08 23:22:29 -05:00
parent 7e96c1b0e0
commit 1b852bceb0
4 changed files with 10 additions and 10 deletions
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5
fs/sysfs/mount.c
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@@ -31,9 +31,6 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
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_type = {
.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)