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SubjectRe: [PATCH v1 3/4] signal: support CLONE_PIDFD with pidfd_send_signal
On Wed, Apr 17, 2019 at 04:01:06PM +0200, Oleg Nesterov wrote:
> On 04/16, Christian Brauner wrote:
> >
> > @@ -3581,12 +3588,12 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
> > if (flags)
> > return -EINVAL;
> >
> > - f = fdget_raw(pidfd);
> > + f = fdget(pidfd);
>
> could you explain this change?
>
> I am just curious, I don't understand why should we disallow O_PATH and how
> this connects to this patch.

Sending a signal through a pidfd is considered to be on a par with a
"write" to that pidfd.
Additionally, we use the fops associated with the fd to detect whether
it is actually a pidfd or not. This is not possible with O_PATH since
f_ops will be set to dummy fops. So we already correctly error out since
we detect that it is an O_PATH before fdget_raw(). This just takes the
opportunity to fix it.

Christian

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