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Message-Id: <20250325184258.2152379-1-sashal@kernel.org>
Date: Tue, 25 Mar 2025 14:42:55 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
stable@...r.kernel.org
Cc: Oliver Hartkopp <socketcan@...tkopp.net>,
syzbot+78ce4489b812515d5e4d@...kaller.appspotmail.com,
Vincent Mailhol <mailhol.vincent@...adoo.fr>,
Marc Kleine-Budde <mkl@...gutronix.de>,
Sasha Levin <sashal@...nel.org>,
linux-can@...r.kernel.org
Subject: [PATCH AUTOSEL 6.1 1/3] can: statistics: use atomic access in hot path
From: Oliver Hartkopp <socketcan@...tkopp.net>
[ Upstream commit 80b5f90158d1364cbd80ad82852a757fc0692bf2 ]
In can_send() and can_receive() CAN messages and CAN filter matches are
counted to be visible in the CAN procfs files.
KCSAN detected a data race within can_send() when two CAN frames have
been generated by a timer event writing to the same CAN netdevice at the
same time. Use atomic operations to access the statistics in the hot path
to fix the KCSAN complaint.
Reported-by: syzbot+78ce4489b812515d5e4d@...kaller.appspotmail.com
Closes: https://lore.kernel.org/all/67cd717d.050a0220.e1a89.0006.GAE@google.com
Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Link: https://patch.msgid.link/20250310143353.3242-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
net/can/af_can.c | 12 ++++++------
net/can/af_can.h | 12 ++++++------
net/can/proc.c | 46 +++++++++++++++++++++++++++-------------------
3 files changed, 39 insertions(+), 31 deletions(-)
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 7d8543e877b44..bbd8e959137d9 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -287,8 +287,8 @@ int can_send(struct sk_buff *skb, int loop)
netif_rx(newskb);
/* update statistics */
- pkg_stats->tx_frames++;
- pkg_stats->tx_frames_delta++;
+ atomic_long_inc(&pkg_stats->tx_frames);
+ atomic_long_inc(&pkg_stats->tx_frames_delta);
return 0;
@@ -648,8 +648,8 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
int matches;
/* update statistics */
- pkg_stats->rx_frames++;
- pkg_stats->rx_frames_delta++;
+ atomic_long_inc(&pkg_stats->rx_frames);
+ atomic_long_inc(&pkg_stats->rx_frames_delta);
/* create non-zero unique skb identifier together with *skb */
while (!(can_skb_prv(skb)->skbcnt))
@@ -670,8 +670,8 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
consume_skb(skb);
if (matches > 0) {
- pkg_stats->matches++;
- pkg_stats->matches_delta++;
+ atomic_long_inc(&pkg_stats->matches);
+ atomic_long_inc(&pkg_stats->matches_delta);
}
}
diff --git a/net/can/af_can.h b/net/can/af_can.h
index 7c2d9161e2245..22f3352c77fec 100644
--- a/net/can/af_can.h
+++ b/net/can/af_can.h
@@ -66,9 +66,9 @@ struct receiver {
struct can_pkg_stats {
unsigned long jiffies_init;
- unsigned long rx_frames;
- unsigned long tx_frames;
- unsigned long matches;
+ atomic_long_t rx_frames;
+ atomic_long_t tx_frames;
+ atomic_long_t matches;
unsigned long total_rx_rate;
unsigned long total_tx_rate;
@@ -82,9 +82,9 @@ struct can_pkg_stats {
unsigned long max_tx_rate;
unsigned long max_rx_match_ratio;
- unsigned long rx_frames_delta;
- unsigned long tx_frames_delta;
- unsigned long matches_delta;
+ atomic_long_t rx_frames_delta;
+ atomic_long_t tx_frames_delta;
+ atomic_long_t matches_delta;
};
/* persistent statistics */
diff --git a/net/can/proc.c b/net/can/proc.c
index bbce97825f13f..25fdf060e30d0 100644
--- a/net/can/proc.c
+++ b/net/can/proc.c
@@ -118,6 +118,13 @@ void can_stat_update(struct timer_list *t)
struct can_pkg_stats *pkg_stats = net->can.pkg_stats;
unsigned long j = jiffies; /* snapshot */
+ long rx_frames = atomic_long_read(&pkg_stats->rx_frames);
+ long tx_frames = atomic_long_read(&pkg_stats->tx_frames);
+ long matches = atomic_long_read(&pkg_stats->matches);
+ long rx_frames_delta = atomic_long_read(&pkg_stats->rx_frames_delta);
+ long tx_frames_delta = atomic_long_read(&pkg_stats->tx_frames_delta);
+ long matches_delta = atomic_long_read(&pkg_stats->matches_delta);
+
/* restart counting in timer context on user request */
if (user_reset)
can_init_stats(net);
@@ -127,35 +134,33 @@ void can_stat_update(struct timer_list *t)
can_init_stats(net);
/* prevent overflow in calc_rate() */
- if (pkg_stats->rx_frames > (ULONG_MAX / HZ))
+ if (rx_frames > (LONG_MAX / HZ))
can_init_stats(net);
/* prevent overflow in calc_rate() */
- if (pkg_stats->tx_frames > (ULONG_MAX / HZ))
+ if (tx_frames > (LONG_MAX / HZ))
can_init_stats(net);
/* matches overflow - very improbable */
- if (pkg_stats->matches > (ULONG_MAX / 100))
+ if (matches > (LONG_MAX / 100))
can_init_stats(net);
/* calc total values */
- if (pkg_stats->rx_frames)
- pkg_stats->total_rx_match_ratio = (pkg_stats->matches * 100) /
- pkg_stats->rx_frames;
+ if (rx_frames)
+ pkg_stats->total_rx_match_ratio = (matches * 100) / rx_frames;
pkg_stats->total_tx_rate = calc_rate(pkg_stats->jiffies_init, j,
- pkg_stats->tx_frames);
+ tx_frames);
pkg_stats->total_rx_rate = calc_rate(pkg_stats->jiffies_init, j,
- pkg_stats->rx_frames);
+ rx_frames);
/* calc current values */
- if (pkg_stats->rx_frames_delta)
+ if (rx_frames_delta)
pkg_stats->current_rx_match_ratio =
- (pkg_stats->matches_delta * 100) /
- pkg_stats->rx_frames_delta;
+ (matches_delta * 100) / rx_frames_delta;
- pkg_stats->current_tx_rate = calc_rate(0, HZ, pkg_stats->tx_frames_delta);
- pkg_stats->current_rx_rate = calc_rate(0, HZ, pkg_stats->rx_frames_delta);
+ pkg_stats->current_tx_rate = calc_rate(0, HZ, tx_frames_delta);
+ pkg_stats->current_rx_rate = calc_rate(0, HZ, rx_frames_delta);
/* check / update maximum values */
if (pkg_stats->max_tx_rate < pkg_stats->current_tx_rate)
@@ -168,9 +173,9 @@ void can_stat_update(struct timer_list *t)
pkg_stats->max_rx_match_ratio = pkg_stats->current_rx_match_ratio;
/* clear values for 'current rate' calculation */
- pkg_stats->tx_frames_delta = 0;
- pkg_stats->rx_frames_delta = 0;
- pkg_stats->matches_delta = 0;
+ atomic_long_set(&pkg_stats->tx_frames_delta, 0);
+ atomic_long_set(&pkg_stats->rx_frames_delta, 0);
+ atomic_long_set(&pkg_stats->matches_delta, 0);
/* restart timer (one second) */
mod_timer(&net->can.stattimer, round_jiffies(jiffies + HZ));
@@ -214,9 +219,12 @@ static int can_stats_proc_show(struct seq_file *m, void *v)
struct can_rcv_lists_stats *rcv_lists_stats = net->can.rcv_lists_stats;
seq_putc(m, '\n');
- seq_printf(m, " %8ld transmitted frames (TXF)\n", pkg_stats->tx_frames);
- seq_printf(m, " %8ld received frames (RXF)\n", pkg_stats->rx_frames);
- seq_printf(m, " %8ld matched frames (RXMF)\n", pkg_stats->matches);
+ seq_printf(m, " %8ld transmitted frames (TXF)\n",
+ atomic_long_read(&pkg_stats->tx_frames));
+ seq_printf(m, " %8ld received frames (RXF)\n",
+ atomic_long_read(&pkg_stats->rx_frames));
+ seq_printf(m, " %8ld matched frames (RXMF)\n",
+ atomic_long_read(&pkg_stats->matches));
seq_putc(m, '\n');
--
2.39.5
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