ipv4: fix dst race in sk_dst_get()

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[ Upstream commit f886497212 ]

When IP route cache had been removed in linux-3.6, we broke assumption
that dst entries were all freed after rcu grace period. DST_NOCACHE
dst were supposed to be freed from dst_release(). But it appears
we want to keep such dst around, either in UDP sockets or tunnels.

In sk_dst_get() we need to make sure dst refcount is not 0
before incrementing it, or else we might end up freeing a dst
twice.

DST_NOCACHE set on a dst does not mean this dst can not be attached
to a socket or a tunnel.

Then, before actual freeing, we need to observe a rcu grace period
to make sure all other cpus can catch the fact the dst is no longer
usable.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dormando <dormando@rydia.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Eric Dumazet 2014-06-24 10:05:11 -07:00 • committed by Greg Kroah-Hartman

parent 10bc26ecaf

commit df90819daf

3 changed files with 18 additions and 16 deletions

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4

include/net/sock.h

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16

net/core/dst.c

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14

net/ipv4/ip_tunnel.c

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