Description
In the Linux kernel, the following vulnerability has been resolved: vxlan: reject dynamic fdb entries that reference a nexthop id The commit cited in the Fixes tag allowed VXLAN FDB entries to point to FDB nexthops so that overlay traffic could be load balanced across multiple VTEPs. Such entries can only be configured from user space, cannot be learned and cannot roam. They only make sense with a user space control plane such as E-VPN where data plane learning is disabled. Despite that, the VXLAN driver does not currently prevent such entries from being configured with the "dynamic" flag. The per-nexthop FDB list is only protected by the per-device hash lock, which is not sufficient when two VXLAN devices point to the same FDB nexthop and therefore share the list. Aging runs in softirq context without RTNL, so an entry deleted by one device can race with an addition or deletion from the other, leading to list corruption: list_del corruption. next->prev should be ffff8881069d9548, but was dead000000000122. (next=ffff8881069d9448) WARNING: CPU: 0 PID: 90 at lib/list_debug.c:65 __list_del_entry_valid_or_report+0x1aa/0x210 ... vxlan_fdb_destroy+0x5b8/0xad0 vxlan_cleanup+0x328/0x450 call_timer_fn+0x2a/0x1c0 run_timer_softirq+0x18c/0x210 BUG: KASAN: slab-use-after-free in vxlan_fdb_destroy Fix this by rejecting the bogus configuration of dynamic FDB entries that point to FDB nexthops, both when created and when an existing entry is updated. As such, the per-nexthop FDB list is only ever mutated under the RTNL lock. Add test cases to make sure that this does not regress in the future.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
1274e1cc42264d4e629841e4f182795cb0becfd2 to < 00c7f4b8144e535ffb931ad45942a1bd1315b882affected1274e1cc42264d4e629841e4f182795cb0becfd2 to < 55a33882808f1402052d53a08ead59aff8af18a1affected1274e1cc42264d4e629841e4f182795cb0becfd2 to < c8f29af91e0830fdabc9aa1eb1a0f898ce1bc603affected1274e1cc42264d4e629841e4f182795cb0becfd2 to < b2a8e165ddb6cd72176890b2954c52b0f6dbce1aaffected1274e1cc42264d4e629841e4f182795cb0becfd2 to < 28f86eec851b7406a4bc6143f82aeba2882d9842affected1274e1cc42264d4e629841e4f182795cb0becfd2 to < 53359916ceb649b7e6947c8c2f669368a41c1354affected1274e1cc42264d4e629841e4f182795cb0becfd2 to < 3fa64d86fc64eda104e3e97721a12a42a2fd2073affected1274e1cc42264d4e629841e4f182795cb0becfd2 to < 98fc57d167446b95b4e719815fe79edef93f8e7aaffected
Linux Linux
Default version status: affected
5.8affected0 to < 5.8unaffected5.10.271 to ≤ 5.10.*unaffected5.15.222 to ≤ 5.15.*unaffected6.1.189 to ≤ 6.1.*unaffected6.6.158 to ≤ 6.6.*unaffected6.12.111 to ≤ 6.12.*unaffected6.18.53 to ≤ 6.18.*unaffected7.2.7 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/00c7f4b8144e535ffb931ad45942a1bd1315b882 ↗
- https://git.kernel.org/stable/c/55a33882808f1402052d53a08ead59aff8af18a1 ↗
- https://git.kernel.org/stable/c/c8f29af91e0830fdabc9aa1eb1a0f898ce1bc603 ↗
- https://git.kernel.org/stable/c/b2a8e165ddb6cd72176890b2954c52b0f6dbce1a ↗
- https://git.kernel.org/stable/c/28f86eec851b7406a4bc6143f82aeba2882d9842 ↗
- https://git.kernel.org/stable/c/53359916ceb649b7e6947c8c2f669368a41c1354 ↗
- https://git.kernel.org/stable/c/3fa64d86fc64eda104e3e97721a12a42a2fd2073 ↗
- https://git.kernel.org/stable/c/98fc57d167446b95b4e719815fe79edef93f8e7a ↗