Problem:
Most target types in the CCID3 code are u32, so subtle conversion errors
can occur if signed time calculations yield negative results: the original
values are lost in the conversion to unsigned, calculation errors go undetected.
This patch therefore
* sets all critical time types from unsigned to suseconds_t
* avoids comparison between signed/unsigned via type-casting
* provides ample warning messages in case time calculations are negative
These warning messages can be removed at a later stage when the code
has undergone more testing.
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
Acked-by: Ian McDonald <ian.mcdonald@xxxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxx>
---
net/dccp/ccids/ccid3.c | 56 +++++++++++++++++++++++++++---------------------
net/dccp/dccp.h | 1 +
2 files changed, 33 insertions(+), 24 deletions(-)
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 89ef118..820bc25 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -128,8 +128,8 @@ static void ccid3_hc_tx_update_x(struct
hctx->ccid3hctx_x = max_t(u64, hctx->ccid3hctx_x,
(hctx->ccid3hctx_s << 6)/TFRC_T_MBI);
- } else if (timeval_delta(now, &hctx->ccid3hctx_t_ld) >=
- hctx->ccid3hctx_rtt) {
+ } else if (timeval_delta(now, &hctx->ccid3hctx_t_ld) -
+ (suseconds_t)hctx->ccid3hctx_rtt >= 0 ) {
hctx->ccid3hctx_x = max(2 * min(hctx->ccid3hctx_x,
hctx->ccid3hctx_x_recv),
@@ -271,7 +271,7 @@ static int ccid3_hc_tx_send_packet(struc
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
struct dccp_tx_hist_entry *new_packet;
struct timeval now;
- long delay;
+ suseconds_t delay;
BUG_ON(hctx == NULL);
@@ -331,7 +331,7 @@ static int ccid3_hc_tx_send_packet(struc
* else
* // send the packet in (t_nom - t_now) milliseconds.
*/
- if (delay - (long)hctx->ccid3hctx_delta >= 0)
+ if (delay - (suseconds_t)hctx->ccid3hctx_delta >= 0)
return delay / 1000L;
break;
case TFRC_SSTATE_TERM:
@@ -353,7 +353,7 @@ static void ccid3_hc_tx_packet_sent(stru
const struct dccp_sock *dp = dccp_sk(sk);
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
struct timeval now;
- unsigned long quarter_rtt;
+ suseconds_t quarter_rtt;
struct dccp_tx_hist_entry *packet;
BUG_ON(hctx == NULL);
@@ -450,10 +450,8 @@ static void ccid3_hc_tx_packet_recv(stru
r_sample = timeval_delta(&now, &packet->dccphtx_tstamp);
t_elapsed = dp->dccps_options_received.dccpor_elapsed_time * 10;
- if (unlikely(r_sample <= 0)) {
- DCCP_WARN("WARNING: R_sample (%ld) <= 0!\n", r_sample);
- r_sample = 0;
- } else if (unlikely(r_sample <= t_elapsed))
+ DCCP_BUG_ON(r_sample < 0);
+ if (unlikely(r_sample <= t_elapsed))
DCCP_WARN("WARNING: r_sample=%ldus <= t_elapsed=%ldus\n",
r_sample, t_elapsed);
else
@@ -698,6 +696,7 @@ static void ccid3_hc_rx_send_feedback(st
struct dccp_sock *dp = dccp_sk(sk);
struct dccp_rx_hist_entry *packet;
struct timeval now;
+ suseconds_t delta;
ccid3_pr_debug("%s, sk=%p\n", dccp_role(sk), sk);
@@ -707,12 +706,12 @@ static void ccid3_hc_rx_send_feedback(st
case TFRC_RSTATE_NO_DATA:
hcrx->ccid3hcrx_x_recv = 0;
break;
- case TFRC_RSTATE_DATA: {
- const u32 delta = timeval_delta(&now,
- &hcrx->ccid3hcrx_tstamp_last_feedback);
+ case TFRC_RSTATE_DATA:
+ delta = timeval_delta(&now,
+ &hcrx->ccid3hcrx_tstamp_last_feedback);
+ DCCP_BUG_ON(delta < 0);
hcrx->ccid3hcrx_x_recv =
scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
- }
break;
case TFRC_RSTATE_TERM:
DCCP_BUG("Illegal %s state TERM, sk=%p", dccp_role(sk), sk);
@@ -730,9 +729,10 @@ static void ccid3_hc_rx_send_feedback(st
hcrx->ccid3hcrx_ccval_last_counter = packet->dccphrx_ccval;
hcrx->ccid3hcrx_bytes_recv = 0;
- /* Convert to multiples of 10us */
- hcrx->ccid3hcrx_elapsed_time =
- timeval_delta(&now, &packet->dccphrx_tstamp) / 10;
+ /* Elapsed time information [RFC 4340, 13.2] in units of 10 * usecs */
+ delta = timeval_delta(&now, &packet->dccphrx_tstamp);
+ DCCP_BUG_ON(delta < 0);
+ hcrx->ccid3hcrx_elapsed_time = delta / 10;
if (hcrx->ccid3hcrx_p == 0)
hcrx->ccid3hcrx_pinv = ~0U; /* see RFC 4342, 8.5 */
@@ -785,7 +785,8 @@ static u32 ccid3_hc_rx_calc_first_li(str
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
- u32 rtt, delta, x_recv, p;
+ u32 x_recv, p;
+ suseconds_t rtt, delta;
struct timeval tstamp = { 0, };
int interval = 0;
int win_count = 0;
@@ -830,8 +831,12 @@ found:
DCCP_CRIT("tail is null\n");
return ~0;
}
- rtt = timeval_delta(&tstamp, &tail->dccphrx_tstamp) * 4 / interval;
- ccid3_pr_debug("%s, sk=%p, approximated RTT to %uus\n",
+
+ delta = timeval_delta(&tstamp, &tail->dccphrx_tstamp);
+ DCCP_BUG_ON(delta < 0);
+
+ rtt = delta * 4 / interval;
+ ccid3_pr_debug("%s, sk=%p, approximated RTT to %ldus\n",
dccp_role(sk), sk, rtt);
/*
@@ -849,8 +854,9 @@ found:
dccp_timestamp(sk, &tstamp);
delta = timeval_delta(&tstamp, &hcrx->ccid3hcrx_tstamp_last_feedback);
- x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
+ DCCP_BUG_ON(delta <= 0);
+ x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
if (x_recv == 0) { /* would also trigger divide-by-zero */
DCCP_WARN("X_recv==0\n");
if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) {
@@ -977,7 +983,8 @@ static void ccid3_hc_rx_packet_recv(stru
const struct dccp_options_received *opt_recv;
struct dccp_rx_hist_entry *packet;
struct timeval now;
- u32 p_prev, rtt_prev, r_sample, t_elapsed;
+ u32 p_prev, rtt_prev;
+ suseconds_t r_sample, t_elapsed;
int loss, payload_size;
BUG_ON(hcrx == NULL);
@@ -997,8 +1004,9 @@ static void ccid3_hc_rx_packet_recv(stru
r_sample = timeval_usecs(&now);
t_elapsed = opt_recv->dccpor_elapsed_time * 10;
+ DCCP_BUG_ON(r_sample < 0);
if (unlikely(r_sample <= t_elapsed))
- DCCP_WARN("r_sample=%uus, t_elapsed=%uus\n",
+ DCCP_WARN("r_sample=%ldus, t_elapsed=%ldus\n",
r_sample, t_elapsed);
else
r_sample -= t_elapsed;
@@ -1051,8 +1059,8 @@ static void ccid3_hc_rx_packet_recv(stru
break;
dccp_timestamp(sk, &now);
- if (timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) >=
- hcrx->ccid3hcrx_rtt) {
+ if (timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) -
+ (suseconds_t)hcrx->ccid3hcrx_rtt >= 0) {
hcrx->ccid3hcrx_tstamp_last_ack = now;
ccid3_hc_rx_send_feedback(sk);
}
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 44829d6..a0900bf 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -432,6 +432,7 @@ static inline void timeval_sub_usecs(str
tv->tv_sec--;
tv->tv_usec += USEC_PER_SEC;
}
+ DCCP_BUG_ON(tv->tv_sec < 0);
}
#ifdef CONFIG_SYSCTL
--
1.4.2.1.g3d5c
-
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