From: Jason Wessel Date: Fri, 29 May 2009 18:34:17 +0000 (-0500) Subject: USB: usb_serial: only allow sysrq on a console port X-Git-Tag: firefly_0821_release~13894^2~51 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=568d422e9cf52b7b26d2e026ae1617971f62b560;p=firefly-linux-kernel-4.4.55.git USB: usb_serial: only allow sysrq on a console port The only time a sysrq should get processed is if the attached device is a console. This is intended to protect sysrq execution on a host connected with a terminal program. Here is the problem scenario: host A <-- rs232 link --> host B Host A is using mincom and a usb pl2303 device to connect to host b which is a linux system with a usb pl2303 device acting as the serial console. When host B is rebooted the pl2303 emits random junk characters on reset. These character sequences contain serial break signals most of the time and when translated to a sysrq have caused host A to get random processes killed, reboots or power down. It is true that in this setup with this patch host B might still have the same problem as host A if you reboot host A. In most cases host A is a development host which seldom gets rebooted, and you could turn off sysrq temporarily on host B if you need to reboot host A. Signed-off-by: Jason Wessel Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c index 9fccc26235a2..8dabac1929b0 100644 --- a/drivers/usb/serial/generic.c +++ b/drivers/usb/serial/generic.c @@ -528,7 +528,7 @@ void usb_serial_generic_unthrottle(struct tty_struct *tty) int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch) { - if (port->sysrq) { + if (port->sysrq && port->console) { if (ch && time_before(jiffies, port->sysrq)) { handle_sysrq(ch, tty_port_tty_get(&port->port)); port->sysrq = 0;