Messages in this thread | | | Date | Wed, 7 Aug 2019 18:21:12 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v3 1/2] fork: extend clone3() to support CLONE_SET_TID |
| |
On 08/07, Dmitry Safonov wrote: > > On 8/7/19 4:48 PM, Oleg Nesterov wrote: > > On 08/06, Adrian Reber wrote: > >> > >> @@ -2530,12 +2530,14 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > >> struct clone_args __user *uargs, > >> size_t size) > >> { > >> + struct pid_namespace *pid_ns = task_active_pid_ns(current); > >> struct clone_args args; > >> > >> if (unlikely(size > PAGE_SIZE)) > >> return -E2BIG; > >> > >> - if (unlikely(size < sizeof(struct clone_args))) > >> + /* The struct needs to be at least the size of the original struct. */ > >> + if (size < (sizeof(struct clone_args) - sizeof(__aligned_u64))) > >> return -EINVAL; > > > > slightly off-topic, but with or without this patch I do not understand > > -EINVAL. Can't we replace this check with > > > > if (size < sizeof(struct clone_args)) > > memset((void*)&args + size, sizeof(struct clone_args) - size, 0); > > > > ? > > > > this way we can new members at the end of clone_args and this matches > > the "if (size > sizeof(struct clone_args))" block below which promises > > that whatever we add into clone_args a zero value should work. > > What if the size is lesser than offsetof(struct clone_args, stack_size)? > Probably, there should be still a check that it's not lesser than what's > the required minimum..
Not sure I understand... I mean, this doesn't differ from the case when size == sizeof(clone_args) but uargs->stack == NULL ?
> Also note, that (kargs) and (args) are a bit different beasts in this > context.. > kargs lies on the stack and might want to be with zero-initializer > : struct kernel_clone_args kargs = {};
I don't think so. Lets consider this patch which adds the new set_tid into clone_args and kernel_clone_args. copy_clone_args_from_user() does
*kargs = (struct kernel_clone_args){ .flags = args.flags, .pidfd = u64_to_user_ptr(args.pidfd), .child_tid = u64_to_user_ptr(args.child_tid), .parent_tid = u64_to_user_ptr(args.parent_tid), .exit_signal = args.exit_signal, .stack = args.stack, .stack_size = args.stack_size, .tls = args.tls, };
so this patch should simply add
.set_tid = args.set_tid;
at the end. No?
Oleg.
| |