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| author | Eric W. Biederman <ebiederm@xmission.com> | 2013-03-13 11:51:49 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-03-13 15:00:20 -0700 |
| commit | e66eded8309ebf679d3d3c1f5820d1f2ca332c71 (patch) | |
| tree | 768e1d799f6d6a4a7f85f48d9e9fc431dc8d017c /kernel/user_namespace.c | |
| parent | 6c23cbbd5056b155401b0a2b5567d530e6c750c4 (diff) | |
| download | lwn-e66eded8309ebf679d3d3c1f5820d1f2ca332c71.tar.gz lwn-e66eded8309ebf679d3d3c1f5820d1f2ca332c71.zip | |
userns: Don't allow CLONE_NEWUSER | CLONE_FS
Don't allowing sharing the root directory with processes in a
different user namespace. There doesn't seem to be any point, and to
allow it would require the overhead of putting a user namespace
reference in fs_struct (for permission checks) and incrementing that
reference count on practically every call to fork.
So just perform the inexpensive test of forbidding sharing fs_struct
acrosss processes in different user namespaces. We already disallow
other forms of threading when unsharing a user namespace so this
should be no real burden in practice.
This updates setns, clone, and unshare to disallow multiple user
namespaces sharing an fs_struct.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/user_namespace.c')
| -rw-r--r-- | kernel/user_namespace.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 8b650837083e..b14f4d342043 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -21,6 +21,7 @@ #include <linux/uaccess.h> #include <linux/ctype.h> #include <linux/projid.h> +#include <linux/fs_struct.h> static struct kmem_cache *user_ns_cachep __read_mostly; @@ -837,6 +838,9 @@ static int userns_install(struct nsproxy *nsproxy, void *ns) if (atomic_read(¤t->mm->mm_users) > 1) return -EINVAL; + if (current->fs->users != 1) + return -EINVAL; + if (!ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; |