From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 25 Sep 2008 12:51:03 +0000 (+0200)
Subject: ALSA: fix locking in snd_pcm_open*() and snd_rawmidi_open*()
X-Git-Tag: v2.6.27-rc8~14^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=399ccdc1cd4e92e541d4dacbbf18c52bd693418b;p=pandora-kernel.git

ALSA: fix locking in snd_pcm_open*() and snd_rawmidi_open*()

The PCM and rawmidi open callbacks have a lock against card->controls_list
but it takes a wrong one, card->controls_rwsem, instead of a right one
card->ctl_files_rwlock.  This patch fixes them.

This change also fixes automatically the potential deadlocks due to
mm->mmap_sem in munmap and copy_from/to_user, reported by Sitsofe
Wheeler:

  A: snd_ctl_elem_user_tlv(): card->controls_rwsem => mm->mmap_sem
  B: snd_pcm_open(): card->open_mutex => card->controls_rwsem
  C: munmap: mm->mmap_sem => snd_pcm_release(): card->open_mutex

The patch breaks the chain.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
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