path: root/kernel/fork.c
diff options
authorEric W. Biederman <>2013-03-13 11:51:49 -0700
committerLinus Torvalds <>2013-03-13 15:00:20 -0700
commite66eded8309ebf679d3d3c1f5820d1f2ca332c71 (patch)
tree768e1d799f6d6a4a7f85f48d9e9fc431dc8d017c /kernel/fork.c
parent6c23cbbd5056b155401b0a2b5567d530e6c750c4 (diff)
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: Signed-off-by: "Eric W. Biederman" <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel/fork.c')
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 8d932b1c9056..1766d324d5e3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1141,6 +1141,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
return ERR_PTR(-EINVAL);
+ return ERR_PTR(-EINVAL);
* Thread groups must share signals as well, and detached threads
* can only be started up within the thread group.
@@ -1807,7 +1810,7 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
* If unsharing a user namespace must also unshare the thread.
if (unshare_flags & CLONE_NEWUSER)
- unshare_flags |= CLONE_THREAD;
+ unshare_flags |= CLONE_THREAD | CLONE_FS;
* If unsharing a pid namespace must also unshare the thread.