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| author | salina@us.ibm.com <salina@us.ibm.com> | 2013-05-07 16:18:09 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-05-16 18:08:58 -0700 |
| commit | 221ba151731133c8b0e1cdb9bfd2a45b3ba8764b (patch) | |
| tree | ba6f1ff35fdc25a3e3a27ba8dc8aceabc8b7e11d /drivers/char | |
| parent | a7b594b4905828b3bfc36be39d48b5e07a23c8e1 (diff) | |
| download | lwn-221ba151731133c8b0e1cdb9bfd2a45b3ba8764b.tar.gz lwn-221ba151731133c8b0e1cdb9bfd2a45b3ba8764b.zip | |
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>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/lp.c | 3 |
1 files changed, 3 insertions, 0 deletions
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; |