linux-kernel - [PATCH 3.16 48/83] ALSA: seq: Fix potential concurrent access to the deleted pool

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1574264230.848071314@decadent.org.uk>
Date:   Wed, 20 Nov 2019 15:37:58 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Takashi Iwai" <tiwai@...e.de>,
        syzbot+4a75454b9ca2777f35c7@...kaller.appspotmail.com
Subject: [PATCH 3.16 48/83] ALSA: seq: Fix potential concurrent access to
 the deleted pool

3.16.78-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

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@...kaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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(-)

--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1911,8 +1911,7 @@ static int snd_seq_ioctl_get_client_pool
 	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;
--- 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_f
 
 	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;
+}
--- 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_se
 /* 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