On Sun, May 26, 2019 at 09:49:14PM -0400, Mike Snitzer wrote:
> On Sun, May 26 2019 at 8:50pm -0400,
> Gen Zhang <blackgod016574@xxxxxxxxx> wrote:
>
> > In function __rh_alloc(), the pointer nreg is allocated a memory space
> > via kmalloc(). And it is used in the following codes. However, when
> > there is a memory allocation error, kmalloc() fails. Thus null pointer
> > dereference may happen. And it will cause the kernel to crash. Therefore,
> > we should check the return value and handle the error.
> > Further, in __rh_find(), we should also check the return value and
> > handle the error.
> >
> > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
> > ---
> > diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c
> > index 1f76045..2fa1641 100644
> > --- a/drivers/md/dm-region-hash.c
> > +++ b/drivers/md/dm-region-hash.c
> > @@ -290,8 +290,11 @@ static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
> > struct dm_region *reg, *nreg;
> >
> > nreg = mempool_alloc(&rh->region_pool, GFP_ATOMIC);
> > - if (unlikely(!nreg))
> > + if (unlikely(!nreg)) {
> > nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);
> > + if (!nreg)
> > + return NULL;
> > + }
> >
> > nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
> > DM_RH_CLEAN : DM_RH_NOSYNC;
>
> This patch isn't needed. __GFP_NOFAIL means the allocation won't fail.
>
> And there are many other users of __GFP_NOFAIL that don't check for
> failure.
>
> Mike
Appreciate your reply, Mike.
Thanks
Gen
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