From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net V3 1/2] ptr_ring: try vmalloc() when kmalloc() fails Date: Thu, 8 Feb 2018 21:17:28 +0200 Message-ID: <20180208211636-mutt-send-email-mst@kernel.org> References: <1518062365-8596-1-git-send-email-jasowang@redhat.com> <20180208063509-mutt-send-email-mst@kernel.org> <2e3978d8-8bf1-2f0c-b446-a5dd65c7ac94@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: netdev@vger.kernel.org To: Jason Wang Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:41934 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751786AbeBHTR3 (ORCPT ); Thu, 8 Feb 2018 14:17:29 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3D8B04023141 for ; Thu, 8 Feb 2018 19:17:29 +0000 (UTC) Content-Disposition: inline In-Reply-To: <2e3978d8-8bf1-2f0c-b446-a5dd65c7ac94@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Feb 08, 2018 at 02:58:40PM +0800, Jason Wang wrote: > > > On 2018年02月08日 12:45, Michael S. Tsirkin wrote: > > On Thu, Feb 08, 2018 at 11:59:24AM +0800, Jason Wang wrote: > > > This patch switch to use kvmalloc_array() for using a vmalloc() > > > fallback to help in case kmalloc() fails. > > > > > > Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com > > > Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers") > > I guess the actual patch is the one that switches tun to ptr_ring. > > I think not, since the issue was large allocation. > > > > > In fact, I think the actual bugfix is patch 2/2. This specific one > > just makes kmalloc less likely to fail but that's > > not what syzbot reported. > > Agree. > > > > > Then I would add this patch on top to make kmalloc less likely to fail. > > Ok. > > > > Signed-off-by: Jason Wang > > > > > > > --- > > > include/linux/ptr_ring.h | 10 +++++----- > > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h > > > index 1883d61..2af71a7 100644 > > > --- a/include/linux/ptr_ring.h > > > +++ b/include/linux/ptr_ring.h > > > @@ -466,7 +466,7 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r, > > > static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp) > > > { > > > - return kcalloc(size, sizeof(void *), gfp); > > > + return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO); > > > } > > > static inline void __ptr_ring_set_size(struct ptr_ring *r, int size) > > This implies a bunch of limitations on the flags. From kvmalloc_node > > docs: > > > > * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported. > > * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is > > * preferable to the vmalloc fallback, due to visible performance drawbacks. > > > > Fine with all the current users, but if we go this way, please add > > documentation so future users don't misuse this API. > > I suspect this is somehow a overkill since this means we need sync with > mm/vmalloc changes in the future to keep it synced. > > > Alternatively, test flags and call kvmalloc or kcalloc? > > Similar to the above issue, I would rather leave it as is. > > Thanks How do we prevent someone from inevitably trying to use this with GFP_ATOMIC? > > > > > > > @@ -601,7 +601,7 @@ static inline int ptr_ring_resize(struct ptr_ring *r, int size, gfp_t gfp, > > > spin_unlock(&(r)->producer_lock); > > > spin_unlock_irqrestore(&(r)->consumer_lock, flags); > > > - kfree(old); > > > + kvfree(old); > > > return 0; > > > } > > > @@ -641,7 +641,7 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, > > > } > > > for (i = 0; i < nrings; ++i) > > > - kfree(queues[i]); > > > + kvfree(queues[i]); > > > kfree(queues); > > > @@ -649,7 +649,7 @@ static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, > > > nomem: > > > while (--i >= 0) > > > - kfree(queues[i]); > > > + kvfree(queues[i]); > > > kfree(queues); > > > @@ -664,7 +664,7 @@ static inline void ptr_ring_cleanup(struct ptr_ring *r, void (*destroy)(void *)) > > > if (destroy) > > > while ((ptr = ptr_ring_consume(r))) > > > destroy(ptr); > > > - kfree(r->queue); > > > + kvfree(r->queue); > > > } > > > #endif /* _LINUX_PTR_RING_H */ > > > -- > > > 2.7.4