Messages in this thread | | | Date | Wed, 11 Sep 2019 15:31:20 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2] fork: check exit_signal passed in clone3() call |
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On 09/10, Eugene Syromiatnikov wrote: > > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -2338,6 +2338,8 @@ struct mm_struct *copy_init_mm(void) > * > * It copies the process, and if successful kick-starts > * it and waits for it to finish using the VM if required. > + * > + * args->exit_signal is expected to be checked for sanity by the caller.
not sure this comment is really useful but it doesn't hurt
> long _do_fork(struct kernel_clone_args *args) > { > @@ -2562,6 +2564,16 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > if (copy_from_user(&args, uargs, size)) > return -EFAULT; > > + /* > + * exit_signal is confined to CSIGNAL mask in legacy syscalls, > + * so it is used unchecked deeper in syscall handling routines; > + * moreover, copying to struct kernel_clone_args.exit_signals > + * trims higher 32 bits, so it is has to be checked that they > + * are zero. > + */ > + if (unlikely(args.exit_signal & ~((u64)CSIGNAL))) > + return -EINVAL;
OK, agreed. As you pointed out, this doesn't guarantee valid_signal(exit_signal). But we do no really care as long as it is non-negative, it acts as exit_signal==0.
I have no idea if we want to deny exit_signal >= _NSIG in clone3(), this was always allowed...
I think this needs the "CC: stable" tag.
Acked-by: Oleg Nesterov <oleg@redhat.com>
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