tree 73b1972219971c25a784019c06ad05b112822468
parent 1a4726ba1dedcdb92bc15a70e65150e9222ceed1
author Mauro Carvalho Chehab <mchehab@s-opensource.com> 1522920652 -0400
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1530609795 +0200

media: dvb_frontend: fix locking issues at dvb_frontend_get_event()

commit 76d81243a487c09619822ef8e7201a756e58a87d upstream.

As warned by smatch:
	drivers/media/dvb-core/dvb_frontend.c:314 dvb_frontend_get_event() warn: inconsistent returns 'sem:&fepriv->sem'.
	  Locked on:   line 288
	               line 295
	               line 306
	               line 314
	  Unlocked on: line 303

The lock implementation for get event is wrong, as, if an
interrupt occurs, down_interruptible() will fail, and the
routine will call up() twice when userspace calls the ioctl
again.

The bad code is there since when Linux migrated to git, in
2005.

Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>