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Commit f2c31e32 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: fix NULL dereferences in check_peer_redir()



Gergely Kalman reported crashes in check_peer_redir().

It appears commit f39925db (ipv4: Cache learned redirect
information in inetpeer.) added a race, leading to possible NULL ptr
dereference.

Since we can now change dst neighbour, we should make sure a reader can
safely use a neighbour.

Add RCU protection to dst neighbour, and make sure check_peer_redir()
can be called safely by different cpus in parallel.

As neighbours are already freed after one RCU grace period, this patch
should not add typical RCU penalty (cache cold effects)

Many thanks to Gergely for providing a pretty report pointing to the
bug.

Reported-by: default avatarGergely Kalman <synapse@hippy.csoma.elte.hu>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 28f4881c
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