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Date: Wed, 5 Jun 2019 08:21:59 -0400 From: Mike Snitzer <snitzer@...hat.com> To: Jiri Slaby <jslaby@...e.cz> Cc: Gen Zhang <blackgod016574@...il.com>, agk@...hat.com, dm-devel@...hat.com, linux-kernel@...r.kernel.org Subject: Re: dm-region-hash: Fix a missing-check bug in __rh_alloc() On Wed, Jun 05 2019 at 2:05am -0400, Jiri Slaby <jslaby@...e.cz> wrote: > On 24. 05. 19, 5:12, Gen Zhang 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@...il.com> > > > > --- > > 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; > > What's the purpose of checking NO_FAIL allocations? There isn't, that was already pointed out in a different thread for this same patch (think patch was posted twice): https://www.redhat.com/archives/dm-devel/2019-May/msg00124.html Mike
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