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authorOleg Nesterov <oleg@redhat.com>2013-09-11 21:19:38 (GMT)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-27 00:18:28 (GMT)
commitf608ebd760cb9b48a333700fdc10245e257d9fce (patch)
tree35afbc0387ba036520881950da155d2a48a585d4 /kernel/fork.c
parent5a48788ca4d6dc78d1856d9ddeea1b1160097cc9 (diff)
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pidns: fix vfork() after unshare(CLONE_NEWPID)
commit e79f525e99b04390ca4d2366309545a836c03bf1 upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 ffbc090..80d92e9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1171,10 +1171,11 @@ 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))
return ERR_PTR(-EINVAL);