Re: [PATCH net] net: vlan: fix a UAF in vlan_dev_real_dev()
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From: Leon Romanovsky <leon@kernel.org>
Date: 2021-10-28 05:45:05
Also in:
linux-rdma, lkml
On Wed, Oct 27, 2021 at 06:46:40PM -0700, Jakub Kicinski wrote:
On Wed, 27 Oct 2021 20:16:06 +0800 Ziyang Xuan wrote:quoted
The real_dev of a vlan net_device may be freed after unregister_vlan_dev(). Access the real_dev continually by vlan_dev_real_dev() will trigger the UAF problem for the real_dev like following: ================================================================== BUG: KASAN: use-after-free in vlan_dev_real_dev+0xf9/0x120 Call Trace: kasan_report.cold+0x83/0xdf vlan_dev_real_dev+0xf9/0x120 is_eth_port_of_netdev_filter.part.0+0xb1/0x2c0 is_eth_port_of_netdev_filter+0x28/0x40 ib_enum_roce_netdev+0x1a3/0x300 ib_enum_all_roce_netdevs+0xc7/0x140 netdevice_event_work_handler+0x9d/0x210 ... Freed by task 9288: kasan_save_stack+0x1b/0x40 kasan_set_track+0x1c/0x30 kasan_set_free_info+0x20/0x30 __kasan_slab_free+0xfc/0x130 slab_free_freelist_hook+0xdd/0x240 kfree+0xe4/0x690 kvfree+0x42/0x50 device_release+0x9f/0x240 kobject_put+0x1c8/0x530 put_device+0x1b/0x30 free_netdev+0x370/0x540 ppp_destroy_interface+0x313/0x3d0 ... Set vlan->real_dev to NULL after dev_put(real_dev) in unregister_vlan_dev(). Check real_dev is not NULL before access it in vlan_dev_real_dev(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: <redacted> Signed-off-by: Ziyang Xuan <redacted> --- net/8021q/vlan.c | 1 + net/8021q/vlan_core.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-)diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c index 55275ef9a31a..1106da84e725 100644 --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c@@ -126,6 +126,7 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head) /* Get rid of the vlan's reference to real_dev */ dev_put(real_dev); + vlan->real_dev = NULL; } int vlan_check_real_dev(struct net_device *real_dev,diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c index 59bc13b5f14f..343f34479d8b 100644 --- a/net/8021q/vlan_core.c +++ b/net/8021q/vlan_core.c@@ -103,7 +103,7 @@ struct net_device *vlan_dev_real_dev(const struct net_device *dev) { struct net_device *ret = vlan_dev_priv(dev)->real_dev; - while (is_vlan_dev(ret)) + while (ret && is_vlan_dev(ret)) ret = vlan_dev_priv(ret)->real_dev; return ret;But will make all the callers of vlan_dev_real_dev() feel like they should NULL-check the result, which is not necessary. RDMA must be calling this helper on a vlan which was already unregistered, can we fix RDMA instead?
He tried to fix RDMA first, but we came to conclusion that we real solution is in netdev land. https://lore.kernel.org/linux-rdma/20211025163941.GA393143@nvidia.com/T/#m44abbf1ea5e4b5237610c1b389c3340d92a03b8d (local) Thanks