Re: [PATCH 1/1] wait: using uninitialized member of wait queue

Evgeny Kuznetsov
2010-10-05T11:05:38Z

Hi,

'wait_queue_t' is passed to prepare_to_wait() function where 'flags' is
used, e.g:
File: /mm/mempool.c
void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
{ .....
.....
init_wait(&wait);
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
.....
}

Best Regards,
Evgeny

On Tue, 2010-10-05 at 12:41 +0200, ext Michał Nazarewicz wrote:
> On Tue, 05 Oct 2010 10:47:57 +0200, Evgeny Kuznetsov
> <EXT-Eugeny.Kuznetsov@nokia.com> wrote:
> > Member "flags" of "wait_queue_t" struct is used in several places
> in
> > kernel code without beeing initialized. "flags" is used in bitwise
> operations.
> ^^^^^^ -- "being"
>
> > If "flags" not initialized then unexpected behaviour may have place.
> > Incorrect flags maybe used later in code.
> > Struct "wait_queue_t" is initialized in function "init_wait()". But
> > "init_wait()" do not initialize "flag" member.
> ^^ -- does ^^^^ -- "flags"
>
> > Added initialization of "wait_queue_t.flags" with zero value into
> "init_wait".
>
> > diff --git a/include/linux/wait.h b/include/linux/wait.h
> > index 0836ccc..3efc9f3 100644
> > --- a/include/linux/wait.h
> > +++ b/include/linux/wait.h
> > @@ -614,6 +614,7 @@ int wake_bit_function(wait_queue_t *wait,
> unsigned mode, int sync, void *key);
> > (wait)->private =
> current; \
> > (wait)->func =
> autoremove_wake_function; \
> > INIT_LIST_HEAD(&(wait)->task_list); \
> > + (wait)->flags =
> 0; \
> > } while (0)
> > /**
>
> I'd turn init_wait() into a static inline. Otherwise looks good to
> me.
> (Interestingly, init_wait() is used only in 3 places in the kernel and
> none uses flags.)
>
> --
> Best regards, _ _
> | Humble Liege of Serenely Enlightened Majesty of o' \,=./ `o
> | Computer Science, Michał "mina86" Nazarewicz (o o)
> +----[mina86*mina86.com]---[mina86*jabber.org]----ooO--(_)--Ooo--