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During removing a bridge device, if the bridge is still up, a new mdb entry
still can be added in br_multicast_add_group() after all mdb entries are
removed in br_multicast_dev_del(). Like the path:
mld_ifc_timer_expire ->
mld_sendpack -> ...
br_multicast_rcv ->
br_multicast_add_group
The new mp's timer will be set up. If the timer expires after the bridge
is freed, it may cause use-after-free panic in br_multicast_group_expired.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
IP: [<ffffffffa07ed2c8>] br_multicast_group_expired+0x28/0xb0 [bridge]
Call Trace:
<IRQ>
[<ffffffff81094536>] call_timer_fn+0x36/0x110
[<ffffffffa07ed2a0>] ? br_mdb_free+0x30/0x30 [bridge]
[<ffffffff81096967>] run_timer_softirq+0x237/0x340
[<ffffffff8108dcbf>] __do_softirq+0xef/0x280
[<ffffffff8169889c>] call_softirq+0x1c/0x30
[<ffffffff8102c275>] do_softirq+0x65/0xa0
[<ffffffff8108e055>] irq_exit+0x115/0x120
[<ffffffff81699515>] smp_apic_timer_interrupt+0x45/0x60
[<ffffffff81697a5d>] apic_timer_interrupt+0x6d/0x80
Nikolay also found it would cause a memory leak - the mdb hash is
reallocated and not freed due to the mdb rehash.
unreferenced object 0xffff8800540ba800 (size 2048):
backtrace:
[<ffffffff816e2287>] kmemleak_alloc+0x67/0xc0
[<ffffffff81260bea>] __kmalloc+0x1ba/0x3e0
[<ffffffffa05c60ee>] br_mdb_rehash+0x5e/0x340 [bridge]
[<ffffffffa05c74af>] br_multicast_new_group+0x43f/0x6e0 [bridge]
[<ffffffffa05c7aa3>] br_multicast_add_group+0x203/0x260 [bridge]
[<ffffffffa05ca4b5>] br_multicast_rcv+0x945/0x11d0 [bridge]
[<ffffffffa05b6b10>] br_dev_xmit+0x180/0x470 [bridge]
[<ffffffff815c781b>] dev_hard_start_xmit+0xbb/0x3d0
[<ffffffff815c8743>] __dev_queue_xmit+0xb13/0xc10
[<ffffffff815c8850>] dev_queue_xmit+0x10/0x20
[<ffffffffa02f8d7a>] ip6_finish_output2+0x5ca/0xac0 [ipv6]
[<ffffffffa02fbfc6>] ip6_finish_output+0x126/0x2c0 [ipv6]
[<ffffffffa02fc245>] ip6_output+0xe5/0x390 [ipv6]
[<ffffffffa032b92c>] NF_HOOK.constprop.44+0x6c/0x240 [ipv6]
[<ffffffffa032bd16>] mld_sendpack+0x216/0x3e0 [ipv6]
[<ffffffffa032d5eb>] mld_ifc_timer_expire+0x18b/0x2b0 [ipv6]
This could happen when ip link remove a bridge or destroy a netns with a
bridge device inside.
With Nikolay's suggestion, this patch is to clean up bridge multicast in
ndo_uninit after bridge dev is shutdown, instead of br_dev_delete, so
that netif_running check in br_multicast_add_group can avoid this issue.
v1->v2:
- fix this issue by moving br_multicast_dev_del to ndo_uninit, instead
of calling dev_close in br_dev_delete.
(NOTE: Depends upon
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.