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Message-Id: <20150708073102.534823313@linuxfoundation.org>
Date: Wed, 8 Jul 2015 00:31:45 -0700
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
Willem de Bruijn <willemb@...gle.com>,
"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.10 05/14] packet: avoid out of bounds read in round robin fanout
3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Willem de Bruijn <willemb@...gle.com>
[ 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@...gle.com>
Signed-off-by: Willem de Bruijn <willemb@...gle.com>
Acked-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/packet/af_packet.c | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1150,16 +1150,6 @@ static void packet_sock_destruct(struct
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)
@@ -1171,13 +1161,9 @@ static unsigned int fanout_demux_lb(stru
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,
--
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