From e3abf92c855c9439f57880b89f1ae8267a99ab45 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Sun, 25 Aug 2019 09:21:44 +0200
Subject: [PATCH] ALSA: seq: Fix potential concurrent access to the deleted
pool
commit 75545304eba6a3d282f923b96a466dc25a81e359 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/core/seq/seq_clientmgr.c | 3 +--
sound/core/seq/seq_fifo.c | 17 +++++++++++++++++
sound/core/seq/seq_fifo.h | 2 ++
3 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 7fa0219c9758..331a2b00e53f 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1906,8 +1906,7 @@ 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;
diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c
index 9acbed1ac982..d9f5428ee995 100644
--- a/sound/core/seq/seq_fifo.c
+++ b/sound/core/seq/seq_fifo.c
@@ -278,3 +278,20 @@ 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;
+}
diff --git a/sound/core/seq/seq_fifo.h b/sound/core/seq/seq_fifo.h
index 062c446e7867..5d38a0d7f0cd 100644
--- a/sound/core/seq/seq_fifo.h
+++ b/sound/core/seq/seq_fifo.h
@@ -68,5 +68,7 @@ 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