On Thu, Mar 07, 2013 at 03:46:24PM -0800, Linus Torvalds wrote:
> On Thu, Mar 7, 2013 at 3:14 PM, Dave Jones <da...@redhat.com> wrote:
> > And.. More fun with pipes.
> > for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
> > 1650: 49 8b 06 mov (%r14),%rax
> >
> > So we got to fasync_remove_entry with a NULL fa struct.
> >
> > Can we just add more NULL checks here, or does that need to happen
> > at a higher level ?
>
> I think you'll find that it's not fapp that was NULL.
yeah, brainfart
> The caller was
> pipe_rdwr_fasync -> fasync_helper, and pipe_rdwr_fasync always passes
> in
>
> &pipe->fasync_readers
>
> (and writers) so it looks like it is pipe that was NULL. Really odd.
> How did the open of the pipe succeed with a NULL i_pipe? We do have
> i_pipe == NULL, but that should happen only with a not-yet-opened
> pipe, or after the last close.
>
> In neither case should you have that pipe_rdwr_fasync() call.
>
> The fact that this happens for a delayed __fput() makes me think it
> was never a successful open to begin with, but how did the FASYNC flag
> get set in that case? Do we actually allow it in the open flags..
> Hmm..
>
> So if we need new NULL pointer checks, I think they'd need to be
> something like the attached patch.
I'll give it a shot. Can't be any worse than what we have already.
> But this is definitely another of those "This is our most desperate
> hour. Help me, Al-biwan Ke-Viro, you're my only hope" issues.
>
> Al? Please don't make me wear that golden bikini.
The box hosting Al's email is down, so you might be making a new fashion
statement
for a little while.
Dave
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