| From | Ben Hutchings <> | Date | Sat, 08 Feb 2020 18:21:22 +0000 | Subject | [PATCH 3.16 143/148] tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() |
| |
3.16.82-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Guillaume Nault <gnault@redhat.com>
commit 721c8dafad26ccfa90ff659ee19755e3377b829d upstream.
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 a0f82f64e269 ("syncookies: remove last_synq_overflow from struct tcp_sock"). But unprotected accesses were already there when timestamp was stored in .last_synq_overflow.
Fixes: 1da177e4c3f4 ("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> [bwh: Backported to 3.16: Use ACCESS_ONCE() instead of {READ,WRITE}_ONCE()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- include/net/tcp.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -482,17 +482,17 @@ struct sock *cookie_v4_check(struct sock */ static inline void tcp_synq_overflow(struct sock *sk) { - unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; + unsigned long last_overflow = ACCESS_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; + ACCESS_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 = ACCESS_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp); return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID); }
|