From: Oleg Nesterov <oleg@redhat.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: linux-kernel@vger.kernel.org, Florian Weimer <fweimer@redhat.com>,
GNU C Library <libc-alpha@sourceware.org>,
Arnd Bergmann <arnd@arndb.de>, Kees Cook <keescook@chromium.org>,
Jann Horn <jannh@google.com>, David Howells <dhowells@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-api@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] clone3: validate stack arguments
Date: Thu, 31 Oct 2019 17:46:53 +0100 [thread overview]
Message-ID: <20191031164653.GA24629@redhat.com> (raw)
In-Reply-To: <20191031113608.20713-1-christian.brauner@ubuntu.com>
On 10/31, Christian Brauner wrote:
>
> --- a/include/uapi/linux/sched.h
> +++ b/include/uapi/linux/sched.h
> @@ -51,6 +51,10 @@
> * sent when the child exits.
> * @stack: Specify the location of the stack for the
> * child process.
> + * Note, @stack is expected to point to the
> + * lowest address. The stack direction will be
> + * determined by the kernel and set up
> + * appropriately based on @stack_size.
I can't review this patch, I have no idea what does stack_size mean
if !arch/x86.
x86 doesn't use stack_size unless a kthread does kernel_thread(), so
this change is probably fine...
Hmm. Off-topic question, why did 7f192e3cd3 ("fork: add clone3") add
"& ~CSIGNAL" in kernel_thread() ? This looks pointless and confusing
to me...
> +static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
> +{
> + if (kargs->stack == 0) {
> + if (kargs->stack_size > 0)
> + return false;
> + } else {
> + if (kargs->stack_size == 0)
> + return false;
So to implement clone3_wrapper(void *bottom_of_stack) you need to do
clone3_wrapper(void *bottom_of_stack)
{
struct clone_args args = {
...
// make clone3_stack_valid() happy
.stack = bottom_of_stack - 1,
.stack_size = 1,
};
}
looks a bit strange. OK, I agree, this example is very artificial.
But why do you think clone3() should nack stack_size == 0 ?
> + if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
> + return false;
Why?
Oleg.
next prev parent reply other threads:[~2019-10-31 16:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-31 11:36 [PATCH] clone3: validate stack arguments Christian Brauner
2019-10-31 11:41 ` David Laight
2019-10-31 13:59 ` Aleksa Sarai
2019-10-31 14:27 ` David Laight
2019-10-31 16:46 ` Oleg Nesterov [this message]
2019-11-01 11:06 ` Christian Brauner
2019-11-01 12:32 ` Oleg Nesterov
2019-11-01 14:40 ` Christian Brauner
2019-11-01 14:57 ` Szabolcs Nagy
2019-11-01 15:10 ` Christian Brauner
2019-11-05 14:23 ` Arnd Bergmann
2019-11-05 20:23 ` Michael Kerrisk (man-pages)
[not found] ` <20191031124037.E26AF20650@mail.kernel.org>
2019-11-06 2:18 ` Christian Brauner
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