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| H A D | neighbour.c | eefb45ee Wed Apr 21 14:42:22 CDT 2021 Chinmay Agarwal <chinagar@codeaurora.org> neighbour: Prevent Race condition in neighbour subsytem
Following Race Condition was detected:
<CPU A, t0>: Executing: __netif_receive_skb() ->__netif_receive_skb_core()
-> arp_rcv() -> arp_process().arp_process() calls __neigh_lookup() which
takes a reference on neighbour entry 'n'.
Moves further along, arp_process() and calls neigh_update()->
__neigh_update(). Neighbour entry is unlocked just before a call to
neigh_update_gc_list.
This unlocking paves way for another thread that may take a reference on
the same and mark it dead and remove it from gc_list.
<CPU B, t1> - neigh_flush_dev() is under execution and calls
neigh_mark_dead(n) marking the neighbour entry 'n' as dead. Also n will be
removed from gc_list.
Moves further along neigh_flush_dev() and calls
neigh_cleanup_and_release(n), but since reference count increased in t1,
'n' couldn't be destroyed.
<CPU A, t3>- Code hits neigh_update_gc_list, with neighbour entry
set as dead.
<CPU A, t4> - arp_process() finally calls neigh_release(n), destroying
the neighbour entry and we have a destroyed ntry still part of gc_list.
Fixes: eb4e8fac00d1("neighbour: Prevent a dead entry from updating gc_list")
Signed-off-by: Chinmay Agarwal <chinagar@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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