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authorWillem de Bruijn <willemb@google.com>2015-06-17 15:59:34 -0400
committerDavid S. Miller <davem@davemloft.net>2015-06-21 10:24:37 -0700
commit468479e6043c84f5a65299cc07cb08a22a28c2b1 (patch)
tree09c287dc76541605f72e2f56cb61317906b56b6a /net/packet/af_packet.c
parent51f458d9612177f69c2e2c437034ae15f93078e7 (diff)
packet: avoid out of bounds read in round robin fanout
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>
Diffstat (limited to 'net/packet/af_packet.c')
-rw-r--r--net/packet/af_packet.c18
1 files changed, 2 insertions, 16 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 131545a06f05..fe1610ddeacf 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1272,16 +1272,6 @@ 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)
@@ -1293,13 +1283,9 @@ 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,