From: salina@us.ibm.com Date: Tue, 7 May 2013 14:18:09 +0000 (+0200) Subject: Char: lp, protect LPGETSTATUS with port_mutex X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=221ba151731133c8b0e1cdb9bfd2a45b3ba8764b;p=linux-beck.git 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 Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/char/lp.c b/drivers/char/lp.c index dafd9ac6428f..0913d79424d3 100644 --- a/drivers/char/lp.c +++ b/drivers/char/lp.c @@ -622,9 +622,12 @@ static int lp_do_ioctl(unsigned int minor, unsigned int cmd, 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;