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4e7655fd4f
The snd_use_lock_sync() (thus its implementation
snd_use_lock_sync_helper()) has the 5 seconds timeout to break out of
the sync loop. It was introduced from the beginning, just to be
"safer", in terms of avoiding the stupid bugs.
However, as Ben Hutchings suggested, this timeout rather introduces a
potential leak or use-after-free that was apparently fixed by the
commit 2d7d54002e ("ALSA: seq: Fix race during FIFO resize"):
for example, snd_seq_fifo_event_in() -> snd_seq_event_dup() ->
copy_from_user() could block for a long time, and snd_use_lock_sync()
goes timeout and still leaves the cell at releasing the pool.
For fixing such a problem, we remove the break by the timeout while
still keeping the warning.
Suggested-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
46 lines
1.5 KiB
C
46 lines
1.5 KiB
C
/*
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* Do sleep inside a spin-lock
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* Copyright (c) 1999 by Takashi Iwai <tiwai@suse.de>
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#include <linux/export.h>
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#include <sound/core.h>
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#include "seq_lock.h"
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#if defined(CONFIG_SMP) || defined(CONFIG_SND_DEBUG)
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/* wait until all locks are released */
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void snd_use_lock_sync_helper(snd_use_lock_t *lockp, const char *file, int line)
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{
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int warn_count = 5 * HZ;
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if (atomic_read(lockp) < 0) {
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pr_warn("ALSA: seq_lock: lock trouble [counter = %d] in %s:%d\n", atomic_read(lockp), file, line);
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return;
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}
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while (atomic_read(lockp) > 0) {
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if (warn_count-- == 0)
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pr_warn("ALSA: seq_lock: waiting [%d left] in %s:%d\n", atomic_read(lockp), file, line);
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schedule_timeout_uninterruptible(1);
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}
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}
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EXPORT_SYMBOL(snd_use_lock_sync_helper);
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#endif
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