linux-kernel - Re: [syzbot] [alsa?] memory leak in snd_seq_create

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Date:   Sun, 16 Jul 2023 15:07:23 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     syzbot <syzbot+cf8e7fa4eeec59b3d485@...kaller.appspotmail.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        perex@...ex.cz, syzkaller-bugs@...glegroups.com, tiwai@...e.com
Subject: Re: [syzbot] [alsa?] memory leak in snd_seq_create_port

On Sun, 16 Jul 2023 10:21:49 +0200,
syzbot wrote:
> 
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    3f01e9fed845 Merge tag 'linux-watchdog-6.5-rc2' of git://w..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14b07344a80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=75da4f0a455bdbd3
> dashboard link: https://syzkaller.appspot.com/bug?extid=cf8e7fa4eeec59b3d485
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15877dc2a80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12905004a80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/441fb7ea58b8/disk-3f01e9fe.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/8fa7790ba0c3/vmlinux-3f01e9fe.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/5e7a6471dadf/bzImage-3f01e9fe.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+cf8e7fa4eeec59b3d485@...kaller.appspotmail.com
> 
> Warning: Permanently added '10.128.1.1' (ED25519) to the list of known hosts.
> executing program
> executing program
> BUG: memory leak
> unreferenced object 0xffff888100877000 (size 512):
>   comm "syz-executor257", pid 5012, jiffies 4294941742 (age 12.790s)
>   hex dump (first 32 bytes):
>     80 ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff8154bf94>] kmalloc_trace+0x24/0x90 mm/slab_common.c:1076
>     [<ffffffff83d29e28>] kmalloc include/linux/slab.h:582 [inline]
>     [<ffffffff83d29e28>] kzalloc include/linux/slab.h:703 [inline]
>     [<ffffffff83d29e28>] snd_seq_create_port+0x78/0x300 sound/core/seq/seq_ports.c:135
>     [<ffffffff83d1f681>] snd_seq_ioctl_create_port+0xe1/0x2a0 sound/core/seq/seq_clientmgr.c:1324
>     [<ffffffff83d20e5e>] snd_seq_ioctl+0x13e/0x290 sound/core/seq/seq_clientmgr.c:2327
>     [<ffffffff81685173>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff81685173>] __do_sys_ioctl fs/ioctl.c:870 [inline]
>     [<ffffffff81685173>] __se_sys_ioctl fs/ioctl.c:856 [inline]
>     [<ffffffff81685173>] __x64_sys_ioctl+0x103/0x140 fs/ioctl.c:856
>     [<ffffffff84a77ff9>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<ffffffff84a77ff9>] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> BUG: memory leak
> unreferenced object 0xffff888106742c00 (size 512):
>   comm "syz-executor257", pid 5013, jiffies 4294942276 (age 7.450s)
>   hex dump (first 32 bytes):
>     80 ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff8154bf94>] kmalloc_trace+0x24/0x90 mm/slab_common.c:1076
>     [<ffffffff83d29e28>] kmalloc include/linux/slab.h:582 [inline]
>     [<ffffffff83d29e28>] kzalloc include/linux/slab.h:703 [inline]
>     [<ffffffff83d29e28>] snd_seq_create_port+0x78/0x300 sound/core/seq/seq_ports.c:135
>     [<ffffffff83d1f681>] snd_seq_ioctl_create_port+0xe1/0x2a0 sound/core/seq/seq_clientmgr.c:1324
>     [<ffffffff83d20e5e>] snd_seq_ioctl+0x13e/0x290 sound/core/seq/seq_clientmgr.c:2327
>     [<ffffffff81685173>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff81685173>] __do_sys_ioctl fs/ioctl.c:870 [inline]
>     [<ffffffff81685173>] __se_sys_ioctl fs/ioctl.c:856 [inline]
>     [<ffffffff81685173>] __x64_sys_ioctl+0x103/0x140 fs/ioctl.c:856
>     [<ffffffff84a77ff9>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<ffffffff84a77ff9>] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Likely a forgotten kfree() at the error path.
The patch below should fix it.


Takashi

-- 8< --
From: Takashi Iwai <tiwai@...e.de>
Subject: [PATCH] ALSA: seq: Fix memory leak at error path in
 snd_seq_create_port()

We forgot to release a newly allocated item at the error path in
snd_seq_create_port().  This patch fixes it.

Reported-by: syzbot+cf8e7fa4eeec59b3d485@...kaller.appspotmail.com
Closes: https://lore.kernel.org/r/00000000000098ed3a0600965f89@google.com
Cc: <stable@...r.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 sound/core/seq/seq_ports.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/core/seq/seq_ports.c b/sound/core/seq/seq_ports.c
index 9b80f8275026..f3f14ff0f80f 100644
--- a/sound/core/seq/seq_ports.c
+++ b/sound/core/seq/seq_ports.c
@@ -149,6 +149,7 @@ int snd_seq_create_port(struct snd_seq_client *client, int port,
 	write_lock_irq(&client->ports_lock);
 	list_for_each_entry(p, &client->ports_list_head, list) {
 		if (p->addr.port == port) {
+			kfree(new_port);
 			num = -EBUSY;
 			goto unlock;
 		}
-- 
2.35.3