Description
In the Linux kernel, the following vulnerability has been resolved: net: bridge: mcast: fix use-after-free of a master VLAN's multicast context br_multicast_toggle_one_vlan() clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before stopping a VLAN's multicast context. That is the teardown handshake: lockless readers gate on the flag through br_multicast_ctx_should_use() -> br_multicast_ctx_vlan_disabled(), so once it is cleared under the lock no reader can arm the context again. For a master VLAN the handshake never runs. __vlan_del() clears BRIDGE_VLAN_INFO_BRENTRY before calling br_vlan_put_master(), so br_multicast_toggle_one_vlan(masterv, false) returns early on !br_vlan_is_brentry(vlan): the flag stays set and br->multicast_lock is never taken. br_vlan_put_master() then drains the context in br_multicast_ctx_deinit() and frees the VLAN through call_rcu(), while a reader still inside rcu_read_lock() sees the context as enabled and re-arms it. The port and port-VLAN branch of the function has no br_vlan_is_brentry() test and flips the flag under br->multicast_lock, so it is not affected. The reader is the bridge transmit path. For a master VLAN br_multicast_rcv() selects brmctx = &vlan->br_mcast_ctx with pmctx = NULL, so IGMP sent to the bridge device re-arms the context's timers after br_multicast_ctx_deinit() has already stopped them. BUG: KASAN: slab-use-after-free in detach_if_pending+0x412/0x4a0 Write of size 8 at addr ffff88810ac39918 by task brmc/601 __mod_timer+0x51a/0xc50 br_multicast_host_join+0x25b/0x390 __br_multicast_add_group+0x468/0x530 br_ip4_multicast_add_group+0x1a0/0x260 br_multicast_rcv+0x2cda/0x61e0 br_dev_xmit+0x6c4/0x1540 Allocated by task 610: br_vlan_add+0x111/0xb40 br_vlan_info+0x370/0x3e0 Freed by task 0: kfree+0x1a7/0x4f0 rcu_core+0x7dc/0x10a0 Only test br_vlan_is_brentry() when enabling, like the br_multicast_ctx_vlan_global_disabled() test next to it. Disabling then always clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before br_multicast_ctx_deinit() drains the context.
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
7b54aaaf53cb784411426c64482af0435f7c845e to < 3afaaee2f972aec9059110953adb62fa3cf5c4bdaffected7b54aaaf53cb784411426c64482af0435f7c845e to < 22226a2c3b90f15b0925f1464470d3baa6c5677eaffected7b54aaaf53cb784411426c64482af0435f7c845e to < 7c54fd8cfbcf371a5ef50db5c53fe6e85fb76686affected7b54aaaf53cb784411426c64482af0435f7c845e to < 3a0ad4fcdfa0b7dba1876de14a12cb65c8b5ca50affected7b54aaaf53cb784411426c64482af0435f7c845e to < c069f29da72324697aa4b7cab5b3647a7d24a575affected7b54aaaf53cb784411426c64482af0435f7c845e to < 3f4752996735e0628af559aa8da1d872c2fac13baffected7b54aaaf53cb784411426c64482af0435f7c845e to < 57f94d3f4dee8b54d63cefddf1112be4656ef9e6affected7b54aaaf53cb784411426c64482af0435f7c845e to < 50e5c6605cc9c2dd57bd2d1b3459674d19738983affected
Linux Linux
Default version status: affected
5.15affected0 to < 5.15unaffected5.15.220 to ≤ 5.15.*unaffected6.1.187 to ≤ 6.1.*unaffected6.6.156 to ≤ 6.6.*unaffected6.12.108 to ≤ 6.12.*unaffected6.18.49 to ≤ 6.18.*unaffected7.1.13 to ≤ 7.1.*unaffected7.2.3 to ≤ 7.2.*unaffected7.3 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/3afaaee2f972aec9059110953adb62fa3cf5c4bd ↗
- https://git.kernel.org/stable/c/22226a2c3b90f15b0925f1464470d3baa6c5677e ↗
- https://git.kernel.org/stable/c/7c54fd8cfbcf371a5ef50db5c53fe6e85fb76686 ↗
- https://git.kernel.org/stable/c/3a0ad4fcdfa0b7dba1876de14a12cb65c8b5ca50 ↗
- https://git.kernel.org/stable/c/c069f29da72324697aa4b7cab5b3647a7d24a575 ↗
- https://git.kernel.org/stable/c/3f4752996735e0628af559aa8da1d872c2fac13b ↗
- https://git.kernel.org/stable/c/57f94d3f4dee8b54d63cefddf1112be4656ef9e6 ↗
- https://git.kernel.org/stable/c/50e5c6605cc9c2dd57bd2d1b3459674d19738983 ↗