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SubjectRe: [PATCH] signalfd: fill in ssi_int for posix timers and message queues
On Mon, 5 Jul 2010, Nathan Lynch wrote:

> Hello Davide,
>
> On Sat, 2010-07-03 at 12:09 -0700, Davide Libenzi wrote:
> > On Fri, 2 Jul 2010, Nathan Lynch wrote:
> >
> > > If signalfd is used to consume a signal generated by a POSIX interval
> > > timer or POSIX message queue, the ssi_int field does not reflect the
> > > data (sigevent->sigev_value) supplied to timer_create(2) or
> > > mq_notify(3). (The ssi_ptr field, however, is filled in.)
> > >
> > > This behavior differs from signalfd's treatment of sigqueue-generated
> > > signals -- see the default case in signalfd_copyinfo. It also gives
> > > results that differ from the case when a signal is handled
> > > conventionally via a sigaction-registered handler.
> > >
> > > So, set signalfd_siginfo->ssi_int in the remaining cases (__SI_TIMER,
> > > __SI_MESGQ) where ssi_ptr is set.
> > >
> > > Signed-off-by: Nathan Lynch <ntl@pobox.com>
> > > ---
> > > fs/signalfd.c | 2 ++
> > > 1 files changed, 2 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/fs/signalfd.c b/fs/signalfd.c
> > > index f329849..1c5a6ad 100644
> > > --- a/fs/signalfd.c
> > > +++ b/fs/signalfd.c
> > > @@ -88,6 +88,7 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
> > > err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
> > > err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
> > > err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
> > > + err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
> > > break;
> > > case __SI_POLL:
> > > err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
> > > @@ -111,6 +112,7 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
> > > err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
> > > err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
> > > err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
> > > + err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
> > > break;
> > > default:
> >
> > I am fine with it, but I now noticed that signalfd_copyinfo() got out of
> > sync from copy_siginfo_to_user(), which should match.
> > Do you mind aligning that too, as part of your patch?
> > An adding a comment on the lines of the one in copy_siginfo_to_user() to
> > signalfd_copyinfo() too?
>
> Sorry, I'm not sure I understand. Are you saying that
> copy_siginfo_to_user should have analogous lines added to assign to
> si_int? That's actually not necessary if I read the code correctly: in
> struct siginfo, si_ptr and si_int are members of a sigval union, so
> assigning to the former covers the latter. signalfd must assign both
> ssi_ptr and ssi_int since they occupy different locations in
> signalfd_siginfo.
>
> Perhaps the attached testcases make the problem (as I see it) more
> clear? The final assertion fails without this patch.

Sorry, my bad. I had forgotten that siginfo had them in a union, so the
different code in signalfd_copyinfo() is needed.
Patch looks fine to me as is.

- Davide




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