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Alexey Kodanev
authored
The following use-after-free was reported by KASan when running
LTP macvtap01 test on 4.16-rc2:
[10642.528443] BUG: KASAN: use-after-free in
macvlan_common_newlink+0x12ef/0x14a0 [macvlan]
[10642.626607] Read of size 8 at addr ffff880ba49f2100 by task ip/18450
...
[10642.963873] Call Trace:
[10642.994352] dump_stack+0x5c/0x7c
[10643.035325] print_address_description+0x75/0x290
[10643.092938] kasan_report+0x28d/0x390
[10643.137971] ? macvlan_common_newlink+0x12ef/0x14a0 [macvlan]
[10643.207963] macvlan_common_newlink+0x12ef/0x14a0 [macvlan]
[10643.275978] macvtap_newlink+0x171/0x260 [macvtap]
[10643.334532] rtnl_newlink+0xd4f/0x1300
...
[10646.256176] Allocated by task 18450:
[10646.299964] kasan_kmalloc+0xa6/0xd0
[10646.343746] kmem_cache_alloc_trace+0xf1/0x210
[10646.397826] macvlan_common_newlink+0x6de/0x14a0 [macvlan]
[10646.464386] macvtap_newlink+0x171/0x260 [macvtap]
[10646.522728] rtnl_newlink+0xd4f/0x1300
...
[10647.022028] Freed by task 18450:
[10647.061549] __kasan_slab_free+0x138/0x180
[10647.111468] kfree+0x9e/0x1c0
[10647.147869] macvlan_port_destroy+0x3db/0x650 [macvlan]
[10647.211411] rollback_registered_many+0x5b9/0xb10
[10647.268715] rollback_registered+0xd9/0x190
[10647.319675] register_netdevice+0x8eb/0xc70
[10647.370635] macvlan_common_newlink+0xe58/0x14a0 [macvlan]
[10647.437195] macvtap_newlink+0x171/0x260 [macvtap]
Commit d02fd6e7 ("macvlan: Fix one possible double free") handles
the case when register_netdevice() invokes ndo_uninit() on error and
as a result free the port. But 'macvlan_port_get_rtnl(dev))' check
(returns dev->rx_handler_data), which was added by this commit in order
to prevent double free, is not quite correct:
* for macvlan it always returns NULL because 'lowerdev' is the one that
was used to register rx handler (port) in macvlan_port_create() as
well as to unregister it in macvlan_port_destroy().
* for macvtap it always returns a valid pointer because macvtap registers
its own rx handler before macvlan_common_newlink().
Fixes: d02fd6e7 ("macvlan: Fix one possible double free")
Signed-off-by: 
Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: 
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