From: Peter Chen Date: Tue, 12 Jun 2018 01:53:01 +0000 (+0800) Subject: usb: typec: tcpm: fix logbuffer index is wrong if _tcpm_log is re-entered X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=d5a4f93511b7000183c0d528739b824752139f79;p=linux.git usb: typec: tcpm: fix logbuffer index is wrong if _tcpm_log is re-entered The port->logbuffer_head may be wrong if the two processes enters _tcpm_log at the mostly same time. The 2nd process enters _tcpm_log before the 1st process update the index, then the 2nd process will not allocate logbuffer, when the 2nd process tries to use log buffer, the index has already updated by the 1st process, so it will get NULL pointer for updated logbuffer, the error message like below: tcpci 0-0050: Log buffer index 6 is NULL Cc: Heikki Krogerus Cc: Guenter Roeck Cc: Jun Li Signed-off-by: Peter Chen Reviewed-by: Heikki Krogerus Cc: stable Reviewed-by: Guenter Roeck Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c index 0dfd755020f43..d961f1ec0e085 100644 --- a/drivers/usb/typec/tcpm.c +++ b/drivers/usb/typec/tcpm.c @@ -418,17 +418,18 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args) u64 ts_nsec = local_clock(); unsigned long rem_nsec; + mutex_lock(&port->logbuffer_lock); if (!port->logbuffer[port->logbuffer_head]) { port->logbuffer[port->logbuffer_head] = kzalloc(LOG_BUFFER_ENTRY_SIZE, GFP_KERNEL); - if (!port->logbuffer[port->logbuffer_head]) + if (!port->logbuffer[port->logbuffer_head]) { + mutex_unlock(&port->logbuffer_lock); return; + } } vsnprintf(tmpbuffer, sizeof(tmpbuffer), fmt, args); - mutex_lock(&port->logbuffer_lock); - if (tcpm_log_full(port)) { port->logbuffer_head = max(port->logbuffer_head - 1, 0); strcpy(tmpbuffer, "overflow");