From 5cec9425b41dcf834c3d48776900d6acb7e96f38 Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Wed, 9 May 2018 14:38:43 +0200 Subject: can: hi311x: Acquire SPI lock on ->do_get_berr_counter hi3110_get_berr_counter() may run concurrently to the rest of the driver but neglects to acquire the lock protecting access to the SPI device. As a result, it and the rest of the driver may clobber each other's tx and rx buffers. We became aware of this issue because transmission of packets with "cangen -g 0 -i -x" frequently hung. It turns out that agetty executes ->do_get_berr_counter every few seconds via the following call stack: CPU: 2 PID: 1605 Comm: agetty [<7f3f7500>] (hi3110_get_berr_counter [hi311x]) [<7f130204>] (can_fill_info [can_dev]) [<80693bc0>] (rtnl_fill_ifinfo) [<806949ec>] (rtnl_dump_ifinfo) [<806b4834>] (netlink_dump) [<806b4bc8>] (netlink_recvmsg) [<8065f180>] (sock_recvmsg) [<80660f90>] (___sys_recvmsg) [<80661e7c>] (__sys_recvmsg) [<80661ec0>] (SyS_recvmsg) [<80108b20>] (ret_fast_syscall+0x0/0x1c) agetty listens to netlink messages in order to update the login prompt when IP addresses change (if /etc/issue contains \4 or \6 escape codes): https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=e36deb6424e8 It's a useful feature, though it seems questionable that it causes CAN bit error statistics to be queried. Be that as it may, if hi3110_get_berr_counter() is invoked while a frame is sent by hi3110_hw_tx(), bogus SPI transfers like the following may occur: => 12 00 (hi3110_get_berr_counter() wanted to transmit EC 00 to query the transmit error counter, but the first byte was overwritten by hi3110_hw_tx_frame()) => EA 00 3E 80 01 FB (hi3110_hw_tx_frame() wanted to transmit a frame, but the first byte was overwritten by hi3110_get_berr_counter() because it wanted to query the receive error counter) This sequence hangs the transmission because the driver believes it has sent a frame and waits for the interrupt signaling completion, but in reality the chip has never sent away the frame since the commands it received were malformed. Fix by acquiring the SPI lock in hi3110_get_berr_counter(). I've scrutinized the entire driver for further unlocked SPI accesses but found no others. Cc: Mathias Duckeck Cc: Akshay Bhat Cc: Casey Fitzpatrick Cc: Stef Walter Cc: Karel Zak Cc: stable@vger.kernel.org # v4.12+ Signed-off-by: Lukas Wunner Reviewed-by: Akshay Bhat Signed-off-by: Marc Kleine-Budde --- drivers/net/can/spi/hi311x.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/net') diff --git a/drivers/net/can/spi/hi311x.c b/drivers/net/can/spi/hi311x.c index 5590c559a8ca..c2cf254e4e95 100644 --- a/drivers/net/can/spi/hi311x.c +++ b/drivers/net/can/spi/hi311x.c @@ -427,8 +427,10 @@ static int hi3110_get_berr_counter(const struct net_device *net, struct hi3110_priv *priv = netdev_priv(net); struct spi_device *spi = priv->spi; + mutex_lock(&priv->hi3110_lock); bec->txerr = hi3110_read(spi, HI3110_READ_TEC); bec->rxerr = hi3110_read(spi, HI3110_READ_REC); + mutex_unlock(&priv->hi3110_lock); return 0; } -- cgit v1.2.3 From 32bee8f48fa048a3198109de50e51c092507ff52 Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Wed, 9 May 2018 14:43:43 +0200 Subject: can: hi311x: Work around TX complete interrupt erratum When sending packets as fast as possible using "cangen -g 0 -i -x", the HI-3110 occasionally latches the interrupt pin high on completion of a packet, but doesn't set the TXCPLT bit in the INTF register. The INTF register contains 0x00 as if no interrupt has occurred. Even waiting for a few milliseconds after the interrupt doesn't help. Work around this apparent erratum by instead checking the TXMTY bit in the STATF register ("TX FIFO empty"). We know that we've queued up a packet for transmission if priv->tx_len is nonzero. If the TX FIFO is empty, transmission of that packet must have completed. Note that this is congruent with our handling of received packets, which likewise gleans from the STATF register whether a packet is waiting in the RX FIFO, instead of looking at the INTF register. Cc: Mathias Duckeck Cc: Akshay Bhat Cc: Casey Fitzpatrick Cc: stable@vger.kernel.org # v4.12+ Signed-off-by: Lukas Wunner Acked-by: Akshay Bhat Signed-off-by: Marc Kleine-Budde --- drivers/net/can/spi/hi311x.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'drivers/net') diff --git a/drivers/net/can/spi/hi311x.c b/drivers/net/can/spi/hi311x.c index c2cf254e4e95..53e320c92a8b 100644 --- a/drivers/net/can/spi/hi311x.c +++ b/drivers/net/can/spi/hi311x.c @@ -91,6 +91,7 @@ #define HI3110_STAT_BUSOFF BIT(2) #define HI3110_STAT_ERRP BIT(3) #define HI3110_STAT_ERRW BIT(4) +#define HI3110_STAT_TXMTY BIT(7) #define HI3110_BTR0_SJW_SHIFT 6 #define HI3110_BTR0_BRP_SHIFT 0 @@ -737,10 +738,7 @@ static irqreturn_t hi3110_can_ist(int irq, void *dev_id) } } - if (intf == 0) - break; - - if (intf & HI3110_INT_TXCPLT) { + if (priv->tx_len && statf & HI3110_STAT_TXMTY) { net->stats.tx_packets++; net->stats.tx_bytes += priv->tx_len - 1; can_led_event(net, CAN_LED_EVENT_TX); @@ -750,6 +748,9 @@ static irqreturn_t hi3110_can_ist(int irq, void *dev_id) } netif_wake_queue(net); } + + if (intf == 0) + break; } mutex_unlock(&priv->hi3110_lock); return IRQ_HANDLED; -- cgit v1.2.3