[PATCH 4.4 14/37] tcp: avoid integer overflows in tcp_rcv_space_adjust()

Greg Kroah-Hartman
2018-06-05T17:29:00Z

From: Eric Dumazet <edumazet@google.com>

commit 607065bad9931e72207b0cac365d7d4abc06bd99 upstream.

When using large tcp_rmem[2] values (I did tests with 500 MB),
I noticed overflows while computing rcvwin.

Lets fix this before the following patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Wei Wang <weiwan@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[Backport: sysctl_tcp_rmem is not Namespace-ify'd in older kernels]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/tcp.h | 2 +-
net/ipv4/tcp_input.c | 10 ++++++----
2 files changed, 7 insertions(+), 5 deletions(-)

--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -324,7 +324,7 @@ struct tcp_sock {

/* Receiver queue space */
struct {
- int space;
+ u32 space;
u32 seq;
u32 time;
} rcvq_space;
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -557,8 +557,8 @@ static inline void tcp_rcv_rtt_measure_t
void tcp_rcv_space_adjust(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
+ u32 copied;
int time;
- int copied;

time = tcp_time_stamp - tp->rcvq_space.time;
if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0)
@@ -580,12 +580,13 @@ void tcp_rcv_space_adjust(struct sock *s

if (sysctl_tcp_moderate_rcvbuf &&
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
- int rcvwin, rcvmem, rcvbuf;
+ int rcvmem, rcvbuf;
+ u64 rcvwin;

/* minimal window to cope with packet losses, assuming
* steady state. Add some cushion because of small variations.
*/
- rcvwin = (copied << 1) + 16 * tp->advmss;
+ rcvwin = ((u64)copied << 1) + 16 * tp->advmss;

/* If rate increased by 25%,
* assume slow start, rcvwin = 3 * copied
@@ -605,7 +606,8 @@ void tcp_rcv_space_adjust(struct sock *s
while (tcp_win_from_space(rcvmem) < tp->advmss)
rcvmem += 128;

- rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]);
+ do_div(rcvwin, tp->advmss);
+ rcvbuf = min_t(u64, rcvwin * rcvmem, sysctl_tcp_rmem[2]);
if (rcvbuf > sk->sk_rcvbuf) {
sk->sk_rcvbuf = rcvbuf;