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authorOleg Nesterov <oleg@redhat.com>2013-09-11 14:19:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:56:19 -0700
commite79f525e99b04390ca4d2366309545a836c03bf1 (patch)
tree06fcca5d6cf0e093b7642f7192bfddc92baed108 /kernel/fork.c
parent3b8967d713d7426e9dd107d065208b84adface91 (diff)
pidns: fix vfork() after unshare(CLONE_NEWPID)
Commit 8382fcac1b81 ("pidns: Outlaw thread creation after unshare(CLONE_NEWPID)") nacks CLONE_VM if the forking process unshared pid_ns, this obviously breaks vfork: int main(void) { assert(unshare(CLONE_NEWUSER | CLONE_NEWPID) == 0); assert(vfork() >= 0); _exit(0); return 0; } fails without this patch. Change this check to use CLONE_SIGHAND instead. This also forbids CLONE_THREAD automatically, and this is what the comment implies. We could probably even drop CLONE_SIGHAND and use CLONE_THREAD, but it would be safer to not do this. The current check denies CLONE_SIGHAND implicitely and there is no reason to change this. Eric said "CLONE_SIGHAND is fine. CLONE_THREAD would be even better. Having shared signal handling between two different pid namespaces is the case that we are fundamentally guarding against." Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Colin Walters <walters@redhat.com> Acked-by: Andy Lutomirski <luto@amacapital.net> Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index c9eaf2013002..3561391ca450 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1173,10 +1173,11 @@ static struct task_struct *copy_process(unsigned long clone_flags,
return ERR_PTR(-EINVAL);
/*
- * If the new process will be in a different pid namespace
- * don't allow the creation of threads.
+ * If the new process will be in a different pid namespace don't
+ * allow it to share a thread group or signal handlers with the
+ * forking task.
*/
- if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
+ if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) &&
(task_active_pid_ns(current) !=
current->nsproxy->pid_ns_for_children))
return ERR_PTR(-EINVAL);