From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: Kmemleak: false-positive in vring_add_indirect ? Date: Fri, 04 Oct 2013 09:29:46 +0930 Message-ID: <87d2nlykgd.fsf@rustcorp.com.au> References: <20131002202047.GA7419@cpaasch-mac> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20131002202047.GA7419@cpaasch-mac> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Christoph Paasch , virtualization@lists.linux-foundation.org Cc: "Michael S. Tsirkin" List-Id: virtualization@lists.linuxfoundation.org Christoph Paasch writes: > Hello, > > I have been hunting a memory-leak warning in vring_add_indirect: > > unreferenced object 0xffff88003d467e20 (size 32): > comm "softirq", pid 0, jiffies 4295197765 (age 6.364s) > hex dump (first 32 bytes): > 28 19 bf 3d 00 00 00 00 0c 00 00 00 01 00 01 00 (..=............ > 02 dc 51 3c 00 00 00 00 56 00 00 00 00 00 00 00 ..Q<....V....... > backtrace: > [] kmemleak_alloc+0x59/0xc0 > [] __kmalloc+0xf3/0x180 > [] vring_add_indirect+0x36/0x280 > [] virtqueue_add_outbuf+0xbf/0x4e0 > [] start_xmit+0x1a0/0x3b0 > [] dev_hard_start_xmit+0x2d1/0x4d0 > [] sch_direct_xmit+0xf2/0x1c0 > [] dev_queue_xmit+0x1c8/0x460 > [] ip6_finish_output2+0x1d7/0x470 > [] ip6_finish_output+0x90/0xb0 > [] ip6_output+0x37/0xb0 > [] igmp6_send+0x2db/0x470 > [] igmp6_timer_handler+0x95/0xa0 > [] call_timer_fn+0x2c/0x90 > [] run_timer_softirq+0x1da/0x1f0 > [] __do_softirq+0xd1/0x1b0 > > May it be that the allocated memory within vring_add_indirect should be marked > as kmemleak_ignore(), because it is mapped from a virtual to a physical > address and thus kmemleak cannot detect that the memory is actually still > being referenced. > > > Thanks for your help, > Christoph Thanks! Does this work? virtio_ring: plug kmemleak false positive. unreferenced object 0xffff88003d467e20 (size 32): comm "softirq", pid 0, jiffies 4295197765 (age 6.364s) hex dump (first 32 bytes): 28 19 bf 3d 00 00 00 00 0c 00 00 00 01 00 01 00 (..=............ 02 dc 51 3c 00 00 00 00 56 00 00 00 00 00 00 00 ..Q<....V....... backtrace: [] kmemleak_alloc+0x59/0xc0 [] __kmalloc+0xf3/0x180 [] vring_add_indirect+0x36/0x280 [] virtqueue_add_outbuf+0xbf/0x4e0 [] start_xmit+0x1a0/0x3b0 [] dev_hard_start_xmit+0x2d1/0x4d0 [] sch_direct_xmit+0xf2/0x1c0 [] dev_queue_xmit+0x1c8/0x460 [] ip6_finish_output2+0x1d7/0x470 [] ip6_finish_output+0x90/0xb0 [] ip6_output+0x37/0xb0 [] igmp6_send+0x2db/0x470 [] igmp6_timer_handler+0x95/0xa0 [] call_timer_fn+0x2c/0x90 [] run_timer_softirq+0x1da/0x1f0 [] __do_softirq+0xd1/0x1b0 Address gets embedded in a descriptor via virt_to_phys(). See detach_buf, which frees it: if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT) kfree(phys_to_virt(vq->vring.desc[i].addr)); Reported-by: Christoph Paasch Fix-suggested-by: Christoph Paasch Typing-done-by: Rusty Russell Signed-off-by: Rusty Russell diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 6b4a4db..6547d46 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -173,6 +173,8 @@ static inline int vring_add_indirect(struct vring_virtqueue *vq, head = vq->free_head; vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT; vq->vring.desc[head].addr = virt_to_phys(desc); + /* kmemleak gives a false positive, as it's hidden by virt_to_phys */ + kmemleak_ignore(desc); vq->vring.desc[head].len = i * sizeof(struct vring_desc); /* Update free pointer */