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authorDaniel Borkmann <dborkman@redhat.com>2013-11-21 16:50:58 +0100
committerDavid S. Miller <davem@davemloft.net>2013-11-21 13:09:43 -0500
commite40526cb20b5ee53419452e1f03d97092f144418 (patch)
tree6e78af9f31887cc85e3137ea11437bbde78515c4 /net/packet/internal.h
parentdb739ef37f07a1a12e388dbaec225d9d9d5d6ded (diff)
packet: fix use after free race in send path when dev is released
Salam reported a use after free bug in PF_PACKET that occurs when we're sending out frames on a socket bound device and suddenly the net device is being unregistered. It appears that commit 827d9780 introduced a possible race condition between {t,}packet_snd() and packet_notifier(). In the case of a bound socket, packet_notifier() can drop the last reference to the net_device and {t,}packet_snd() might end up suddenly sending a packet over a freed net_device. To avoid reverting 827d9780 and thus introducing a performance regression compared to the current state of things, we decided to hold a cached RCU protected pointer to the net device and maintain it on write side via bind spin_lock protected register_prot_hook() and __unregister_prot_hook() calls. In {t,}packet_snd() path, we access this pointer under rcu_read_lock through packet_cached_dev_get() that holds reference to the device to prevent it from being freed through packet_notifier() while we're in send path. This is okay to do as dev_put()/dev_hold() are per-cpu counters, so this should not be a performance issue. Also, the code simplifies a bit as we don't need need_rls_dev anymore. Fixes: 827d978037d7 ("af-packet: Use existing netdev reference for bound sockets.") Reported-by: Salam Noureddine <noureddine@aristanetworks.com> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Salam Noureddine <noureddine@aristanetworks.com> Cc: Ben Greear <greearb@candelatech.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/packet/internal.h')
-rw-r--r--net/packet/internal.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/packet/internal.h b/net/packet/internal.h
index c4e4b4561207..1035fa2d909c 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -113,6 +113,7 @@ struct packet_sock {
unsigned int tp_loss:1;
unsigned int tp_tx_has_off:1;
unsigned int tp_tstamp;
+ struct net_device __rcu *cached_dev;
struct packet_type prot_hook ____cacheline_aligned_in_smp;
};