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[142.167.216.168]) by smtp.gmail.com with ESMTPSA id y25sm408767qkj.35.2019.08.27.15.22.20 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 27 Aug 2019 15:22:20 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1i2jr1-00080x-Hu; Tue, 27 Aug 2019 19:22:19 -0300 Date: Tue, 27 Aug 2019 19:22:19 -0300 From: Jason Gunthorpe To: Ralph Campbell Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, =?utf-8?B?SsOpcsO0bWU=?= Glisse , Andrew Morton , Christoph Hellwig Subject: Re: [PATCH 2/2] mm/hmm: hmm_range_fault() infinite loop Message-ID: <20190827222219.GA30700@ziepe.ca> References: <20190823221753.2514-1-rcampbell@nvidia.com> <20190823221753.2514-3-rcampbell@nvidia.com> <20190827184157.GA24929@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 27, 2019 at 01:16:13PM -0700, Ralph Campbell wrote: > > On 8/27/19 11:41 AM, Jason Gunthorpe wrote: > > On Fri, Aug 23, 2019 at 03:17:53PM -0700, Ralph Campbell wrote: > > > > > Signed-off-by: Ralph Campbell > > > mm/hmm.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/mm/hmm.c b/mm/hmm.c > > > index 29371485fe94..4882b83aeccb 100644 > > > +++ b/mm/hmm.c > > > @@ -292,6 +292,9 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end, > > > hmm_vma_walk->last = addr; > > > i = (addr - range->start) >> PAGE_SHIFT; > > > + if (write_fault && walk->vma && !(walk->vma->vm_flags & VM_WRITE)) > > > + return -EPERM; > > > > Can walk->vma be NULL here? hmm_vma_do_fault() touches it > > unconditionally. > > > > Jason > > > walk->vma can be NULL. hmm_vma_do_fault() no longer touches it > unconditionally, that is what the preceding patch fixes. > I suppose I could change hmm_vma_walk_hole_() to check for NULL > and fill in the pfns[] array, I just chose to handle it in > hmm_vma_do_fault(). Okay, yes maybe long term it would be clearer to do the vma null check closer to the start of the callback, but this is a good enough bug fix Reviewed-by: Jason Gunthorpe Jason