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tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() 

[ Upstream commit 721c8dafad ]

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 a0f82f64e2 ("syncookies: remove last_synq_overflow from
struct tcp_sock"). But unprotected accesses were already there when
timestamp was stored in .last_synq_overflow.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Guillaume Nault 2019-12-06 12:38:49 +01:00 committed by Greg Kroah-Hartman
parent 12f1107bd7
commit b8a3066895
1 changed files with 3 additions and 3 deletions
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6
include/net/tcp.h
View File

@ -500,17 +500,17 @@ 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