RE: [PATCH] hv_netvsc: Fix memory leak when removing rndis device
From: Haiyang Zhang <haiyangz@microsoft.com>
Date: 2020-01-13 19:55:51
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-----Original Message----- From: Mohammed Gamal <redacted> Sent: Monday, January 13, 2020 2:28 PM To: linux-hyperv@vger.kernel.org; Stephen Hemminger [off-list ref]; Haiyang Zhang [off-list ref]; netdev@vger.kernel.org Cc: KY Srinivasan <kys@microsoft.com>; sashal@kernel.org; vkuznets [off-list ref]; cavery [off-list ref]; linux- kernel@vger.kernel.org; Mohammed Gamal [off-list ref] 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-quoted
extension which points to the rndis_device struct to NULL without ever freeingthe structure first, leaving it dangling. This patch fixes this by freeing the structure before setting net_device-quoted
extension to NULLSigned-off-by: Mohammed Gamal <redacted> --- 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