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ALSA: seq: Fix potential concurrent access to the deleted pool 

The input pool of a client might be deleted via the resize ioctl, the
the access to it should be covered by the proper locks.  Currently the
only missing place is the call in snd_seq_ioctl_get_client_pool(), and
this patch papers over it.

Reported-by: syzbot+4a75454b9ca2777f35c7@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2019-08-25 09:21:44 +02:00
parent f9f0e9ed35
commit 75545304eb
3 changed files with 20 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
sound/core/seq/seq_clientmgr.c
View File

@ -1835,8 +1835,7 @@ static int snd_seq_ioctl_get_client_pool(struct snd_seq_client *client,
if (cptr->type == USER_CLIENT) {
info->input_pool = cptr->data.user.fifo_pool_size;
info->input_free = info->input_pool;
if (cptr->data.user.fifo)
info->input_free = snd_seq_unused_cells(cptr->data.user.fifo->pool);
info->input_free = snd_seq_fifo_unused_cells(cptr->data.user.fifo);
} else {
info->input_pool = 0;
info->input_free = 0;

17
sound/core/seq/seq_fifo.c
View File

@ -263,3 +263,20 @@ int snd_seq_fifo_resize(struct snd_seq_fifo *f, int poolsize)
return 0;
}
/* get the number of unused cells safely */
int snd_seq_fifo_unused_cells(struct snd_seq_fifo *f)
{
unsigned long flags;
int cells;
if (!f)
return 0;
snd_use_lock_use(&f->use_lock);
spin_lock_irqsave(&f->lock, flags);
cells = snd_seq_unused_cells(f->pool);
spin_unlock_irqrestore(&f->lock, flags);
snd_use_lock_free(&f->use_lock);
return cells;
}

2
sound/core/seq/seq_fifo.h
View File

@ -53,5 +53,7 @@ int snd_seq_fifo_poll_wait(struct snd_seq_fifo *f, struct file *file, poll_table
/* resize pool in fifo */
int snd_seq_fifo_resize(struct snd_seq_fifo *f, int poolsize);
/* get the number of unused cells safely */
int snd_seq_fifo_unused_cells(struct snd_seq_fifo *f);
#endif