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Commit e7a3b025 authored by Guillaume Nault's avatar Guillaume Nault Committed by Greg Kroah-Hartman
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tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() 



[ Upstream commit 721c8dafad26ccfa90ff659ee19755e3377b829d ]

Syncookies borrow the ->rx_opt.ts_recent_stamp field to store the
timestamp of the last synflood. Protect them with READ_ONCE() and
WRITE_ONCE() since reads and writes aren't serialised.

Use of .rx_opt.ts_recent_stamp for storing the synflood timestamp was
introduced by a0f82f64 ("syncookies: remove last_synq_overflow from
struct tcp_sock"). But unprotected accesses were already there when
timestamp was stored in .last_synq_overflow.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: default avatarGuillaume Nault <gnault@redhat.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0c8cd7f6

include/net/tcp.h

+3 −3
Original line number Diff line number Diff line
@@ -494,17 +494,17 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb); 
 */

static inline void tcp_synq_overflow(const struct sock *sk)

{

	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;

	unsigned long last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);

	unsigned long now = jiffies;



	if (!time_between32(now, last_overflow, last_overflow + HZ))

		tcp_sk(sk)->rx_opt.ts_recent_stamp = now;

		WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now);

}



/* syncookies: no recent synqueue overflow on this listening socket? */

static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)

{

	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;

	unsigned long last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);



	/* If last_overflow <= jiffies <= last_overflow + TCP_SYNCOOKIE_VALID,

	 * then we're under synflood. However, we have to use