Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 468479e6 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

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: dc99f600 ("packet: Add fanout support.")
Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 51f458d9

net/packet/af_packet.c

+2 −16
Original line number Original line Diff line number Diff line
@@ -1272,16 +1272,6 @@ static void packet_sock_destruct(struct sock *sk) 
	sk_refcnt_debug_dec(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,

static unsigned int fanout_demux_hash(struct packet_fanout *f,

				      struct sk_buff *skb,

				      struct sk_buff *skb,

				      unsigned int num)

				      unsigned int num)
@@ -1293,13 +1283,9 @@ static unsigned int fanout_demux_lb(struct packet_fanout *f, 
				    struct sk_buff *skb,

				    struct sk_buff *skb,

				    unsigned int num)

				    unsigned int num)

{

{

	int cur, old;

	unsigned int val = atomic_inc_return(&f->rr_cur);





	cur = atomic_read(&f->rr_cur);

	return val % num;

	while ((old = atomic_cmpxchg(&f->rr_cur, cur,

				     fanout_rr_next(f, num))) != cur)

		cur = old;

	return cur;

}

}





static unsigned int fanout_demux_cpu(struct packet_fanout *f,

static unsigned int fanout_demux_cpu(struct packet_fanout *f,