From: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
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 <jason.wessel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
drivers/usb/serial/generic.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 9fccc26..8dabac1 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;
--
1.6.3.2
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