Char: lp, protect LPGETSTATUS with port_mutex
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>
diff --git a/drivers/char/lp.c b/drivers/char/lp.c
index dafd9ac..0913d79 100644
--- a/drivers/char/lp.c
+++ b/drivers/char/lp.c
@@ -622,9 +622,12 @@
return -EFAULT;
break;
case LPGETSTATUS:
+ if (mutex_lock_interruptible(&lp_table[minor].port_mutex))
+ return -EINTR;
lp_claim_parport_or_block (&lp_table[minor]);
status = r_str(minor);
lp_release_parport (&lp_table[minor]);
+ mutex_unlock(&lp_table[minor].port_mutex);
if (copy_to_user(argp, &status, sizeof(int)))
return -EFAULT;