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    Subject[PATCH 5.10 508/575] net: vlan: fix a UAF in vlan_dev_real_dev()
    Date
    From: Ziyang Xuan <william.xuanziyang@huawei.com>

    [ Upstream commit 563bcbae3ba233c275c244bfce2efe12938f5363 ]

    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
    ...

    Move the put_device(real_dev) to vlan_dev_free(). Ensure
    real_dev not be freed before vlan_dev unregistered.

    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Reported-by: syzbot+e4df4e1389e28972e955@syzkaller.appspotmail.com
    Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
    Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/8021q/vlan.c | 3 ---
    net/8021q/vlan_dev.c | 3 +++
    2 files changed, 3 insertions(+), 3 deletions(-)

    diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
    index 15bbfaf943fd1..ad3780067a7d8 100644
    --- a/net/8021q/vlan.c
    +++ b/net/8021q/vlan.c
    @@ -120,9 +120,6 @@ void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
    }

    vlan_vid_del(real_dev, vlan->vlan_proto, vlan_id);
    -
    - /* Get rid of the vlan's reference to real_dev */
    - dev_put(real_dev);
    }

    int vlan_check_real_dev(struct net_device *real_dev,
    diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
    index ec8408d1638fb..c7eba7dab0938 100644
    --- a/net/8021q/vlan_dev.c
    +++ b/net/8021q/vlan_dev.c
    @@ -813,6 +813,9 @@ static void vlan_dev_free(struct net_device *dev)

    free_percpu(vlan->vlan_pcpu_stats);
    vlan->vlan_pcpu_stats = NULL;
    +
    + /* Get rid of the vlan's reference to real_dev */
    + dev_put(vlan->real_dev);
    }

    void vlan_setup(struct net_device *dev)
    --
    2.33.0


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