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| author | Willem de Bruijn <willemb@google.com> | 2015-06-17 15:59:34 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-07-10 10:37:56 -0700 |
| commit | 4ce9d474d5357852241e982dd5e106aa1b929073 (patch) | |
| tree | 2e0e3c76c4e069d2be2dfc9d2732f2db16c7f9ac | |
| parent | 06f6b596d3bde14318753a243dea62b80b3fc26f (diff) | |
| download | lwn-4ce9d474d5357852241e982dd5e106aa1b929073.tar.gz lwn-4ce9d474d5357852241e982dd5e106aa1b929073.zip | |
packet: avoid out of bounds read in round robin fanout
[ Upstream commit 468479e6043c84f5a65299cc07cb08a22a28c2b1 ]
PACKET_FANOUT_LB computes f->rr_cur such that it is modulo
f->num_members. It returns the old value unconditionally, but
f->num_members may have changed since the last store. Ensure
that the return value is always < num.
When modifying the logic, simplify it further by replacing the loop
with an unconditional atomic increment.
Fixes: dc99f600698d ("packet: Add fanout support.")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | net/packet/af_packet.c | 18 |
1 files changed, 2 insertions, 16 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index f238530bd1b5..84a60b82e235 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1264,16 +1264,6 @@ static void packet_sock_destruct(struct sock *sk) sk_refcnt_debug_dec(sk); } -static int fanout_rr_next(struct packet_fanout *f, unsigned int num) -{ - int x = atomic_read(&f->rr_cur) + 1; - - if (x >= num) - x = 0; - - return x; -} - static unsigned int fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) @@ -1285,13 +1275,9 @@ static unsigned int fanout_demux_lb(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) { - int cur, old; + unsigned int val = atomic_inc_return(&f->rr_cur); - cur = atomic_read(&f->rr_cur); - while ((old = atomic_cmpxchg(&f->rr_cur, cur, - fanout_rr_next(f, num))) != cur) - cur = old; - return cur; + return val % num; } static unsigned int fanout_demux_cpu(struct packet_fanout *f, |