diff options
| author | Willem de Bruijn <willemb@google.com> | 2015-06-17 15:59:34 -0400 |
|---|---|---|
| committer | Zefan Li <lizefan@huawei.com> | 2015-10-22 09:20:05 +0800 |
| commit | 52686b9264cfdff747380f1bb70d11274fd83060 (patch) | |
| tree | 7e967243bf1be385fbf660b7a22edc0f9f2ebacd | |
| parent | 2fb9a78c44b0801fb17f3f73f553b8416b96abe0 (diff) | |
packet: avoid out of bounds read in round robin fanout
commit 468479e6043c84f5a65299cc07cb08a22a28c2b1 upstream.
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>
[lizf: Backported to 3.4:
- adjust context
- fanout_demux_lb() returns a pointer]
Signed-off-by: Zefan Li <lizefan@huawei.com>
| -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 af067d72dff3..79c75e1d17ee 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1169,16 +1169,6 @@ 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 struct sock *fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) { u32 idx, hash = skb->rxhash; @@ -1190,13 +1180,9 @@ static struct sock *fanout_demux_hash(struct packet_fanout *f, struct sk_buff *s static struct sock *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 f->arr[cur]; + return f->arr[val % num]; } static struct sock *fanout_demux_cpu(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) |