The patch fixes a problem in the lp driver that can cause oopses as
follows:
process A: calls lp_write, which in turn calls
parport_ieee1284_write_compat, and that invokes
parport_wait_peripheral
process B: meanwhile does an ioctl(LPGETSTATUS), which call
lp_release_parport when done. This function will set
physport->cad = NULL.
process A: parport_wait_peripheral tries to dereference
physport->cad and dies
So, protect that code with the port_mutex in order to protect against
simultaneous calls to lp_read/lp_write.
Similar protection is probably required for ioctl(LPRESET)...
This patch was done by IBM a while back and we (at suse) have that
since at least 2004 in our repos. Let's make it upstream.
Signed-off-by: okir@suse.de
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
221ba15173