> -----Original Message----- > From: Mohammed Gamal <mgamal@xxxxxxxxxx> > Sent: Monday, January 13, 2020 2:28 PM > To: linux-hyperv@xxxxxxxxxxxxxxx; Stephen Hemminger > <sthemmin@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; > netdev@xxxxxxxxxxxxxxx > Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; sashal@xxxxxxxxxx; vkuznets > <vkuznets@xxxxxxxxxx>; cavery <cavery@xxxxxxxxxx>; linux- > kernel@xxxxxxxxxxxxxxx; Mohammed Gamal <mgamal@xxxxxxxxxx> > Subject: [PATCH] hv_netvsc: Fix memory leak when removing rndis device > > kmemleak detects the following memory leak when hot removing a network > device: > > unreferenced object 0xffff888083f63600 (size 256): > comm "kworker/0:1", pid 12, jiffies 4294831717 (age 1113.676s) > hex dump (first 32 bytes): > 00 40 c7 33 80 88 ff ff 00 00 00 00 10 00 00 00 .@.3............ > 00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N.......... > backtrace: > [<00000000d4a8f5be>] rndis_filter_device_add+0x117/0x11c0 [hv_netvsc] > [<000000009c02d75b>] netvsc_probe+0x5e7/0xbf0 [hv_netvsc] > [<00000000ddafce23>] vmbus_probe+0x74/0x170 [hv_vmbus] > [<00000000046e64f1>] really_probe+0x22f/0xb50 > [<000000005cc35eb7>] driver_probe_device+0x25e/0x370 > [<0000000043c642b2>] bus_for_each_drv+0x11f/0x1b0 > [<000000005e3d09f0>] __device_attach+0x1c6/0x2f0 > [<00000000a72c362f>] bus_probe_device+0x1a6/0x260 > [<0000000008478399>] device_add+0x10a3/0x18e0 > [<00000000cf07b48c>] vmbus_device_register+0xe7/0x1e0 [hv_vmbus] > [<00000000d46cf032>] vmbus_add_channel_work+0x8ab/0x1770 [hv_vmbus] > [<000000002c94bb64>] process_one_work+0x919/0x17d0 > [<0000000096de6781>] worker_thread+0x87/0xb40 > [<00000000fbe7397e>] kthread+0x333/0x3f0 > [<000000004f844269>] ret_from_fork+0x3a/0x50 > > rndis_filter_device_add() allocates an instance of struct rndis_device which > never gets deallocated and rndis_filter_device_remove() sets net_device- > >extension which points to the rndis_device struct to NULL without ever freeing > the structure first, leaving it dangling. > > This patch fixes this by freeing the structure before setting net_device- > >extension to NULL > > Signed-off-by: Mohammed Gamal <mgamal@xxxxxxxxxx> > --- > drivers/net/hyperv/rndis_filter.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c > index 857c4bea451c..d2e094f521a4 100644 > --- a/drivers/net/hyperv/rndis_filter.c > +++ b/drivers/net/hyperv/rndis_filter.c > @@ -1443,6 +1443,7 @@ void rndis_filter_device_remove(struct hv_device > *dev, > /* Halt and release the rndis device */ > rndis_filter_halt_device(net_dev, rndis_dev); > > + kfree(rndis_dev); > net_dev->extension = NULL; The struct rndis_device *should* be freed in free_netvsc_device_rcu() ==> free_netvsc_device(): static void free_netvsc_device(struct rcu_head *head) { struct netvsc_device *nvdev = container_of(head, struct netvsc_device, rcu); int i; kfree(nvdev->extension); So we no longer free it in the rndis_filter_device_remove(). But, the commit 02400fcee2542ee334a2394e0d9f6efd969fe782 did have a bug: Date: Tue, 20 Mar 2018 15:03:03 -0700 [PATCH] hv_netvsc: use RCU to fix concurrent rx and queue changes It should have removed the following line when moving the free() to free_netvsc_device(): > net_dev->extension = NULL; Then, the leak of rndis_dev will be fixed. I suggested you to fix it in this way. Thanks, - Haiyang