tree 8cbb43fd3cda74d80b0540b4d0d5f1b96883d283
parent becf7d87cda9c1afbe187d30590cd2c749bda3b6
author Takashi Iwai <tiwai@suse.de> 1513266252 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1514565779 +0100

ALSA: rawmidi: Avoid racy info ioctl via ctl device

commit c1cfd9025cc394fd137a01159d74335c5ac978ce upstream.

The rawmidi also allows to obtaining the information via ioctl of ctl
API.  It means that user can issue an ioctl to the rawmidi device even
when it's being removed as long as the control device is present.
Although the code has some protection via the global register_mutex,
its range is limited to the search of the corresponding rawmidi
object, and the mutex is already unlocked at accessing the rawmidi
object.  This may lead to a use-after-free.

For avoiding it, this patch widens the application of register_mutex
to the whole snd_rawmidi_info_select() function.  We have another
mutex per rawmidi object, but this operation isn't very hot path, so
it shouldn't matter from the performance POV.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>