[lkml]   [2013]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 01/15] Char: lp, protect LPGETSTATUS with port_mutex
From: "" <>

The patch fixes a problem in the lp driver that can cause oopses as
process A: calls lp_write, which in turn calls
parport_ieee1284_write_compat, and that invokes
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: Jiri Slaby <>
Cc: Arnd Bergmann <>
Cc: Greg Kroah-Hartman <>
drivers/char/lp.c | 3 +++
1 file changed, 3 insertions(+)

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 @@ static int lp_do_ioctl(unsigned int minor, unsigned int cmd,
return -EFAULT;
+ 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;

 \ /
  Last update: 2013-05-07 17:21    [W:0.206 / U:1.304 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site