linux-kernel - [PATCH -next v2] ALSA: seq: fix undefined behavior in bit shift for SNDRV_SEQ_FILTER_USE

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Date:   Mon, 21 Nov 2022 19:16:30 +0800
From:   Baisong Zhong <zhongbaisong@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <alsa-devel@...a-project.org>
CC:     <perex@...ex.cz>, <tiwai@...e.com>, <zhongbaisong@...wei.com>,
        <tiwai@...e.de>
Subject: [PATCH -next v2] ALSA: seq: fix undefined behavior in bit shift for SNDRV_SEQ_FILTER_USE_EVENT

Shifting signed 32-bit value by 31 bits is undefined, so changing
significant bit to unsigned. The UBSAN warning calltrace like below:

UBSAN: shift-out-of-bounds in sound/core/seq/seq_clientmgr.c:509:22
left shift of 1 by 31 places cannot be represented in type 'int'
...
Call Trace:
 <TASK>
 dump_stack_lvl+0x8d/0xcf
 ubsan_epilogue+0xa/0x44
 __ubsan_handle_shift_out_of_bounds+0x1e7/0x208
 snd_seq_deliver_single_event.constprop.21+0x191/0x2f0
 snd_seq_deliver_event+0x1a2/0x350
 snd_seq_kernel_client_dispatch+0x8b/0xb0
 snd_seq_client_notify_subscription+0x72/0xa0
 snd_seq_ioctl_subscribe_port+0x128/0x160
 snd_seq_kernel_client_ctl+0xce/0xf0
 snd_seq_oss_create_client+0x109/0x15b
 alsa_seq_oss_init+0x11c/0x1aa
 do_one_initcall+0x80/0x440
 kernel_init_freeable+0x370/0x3c3
 kernel_init+0x1b/0x190
 ret_from_fork+0x1f/0x30
 </TASK>

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Baisong Zhong <zhongbaisong@...wei.com>
---
v2: update all SNDRV_SEQ_FILTER_* to 1U to keep consistent
---
 include/uapi/sound/asequencer.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/uapi/sound/asequencer.h b/include/uapi/sound/asequencer.h
index 6d4a2c60808d..00d2703e8fca 100644
--- a/include/uapi/sound/asequencer.h
+++ b/include/uapi/sound/asequencer.h
@@ -328,10 +328,10 @@ typedef int __bitwise snd_seq_client_type_t;
 #define	KERNEL_CLIENT	((__force snd_seq_client_type_t) 2)

 	/* event filter flags */
-#define SNDRV_SEQ_FILTER_BROADCAST	(1<<0)	/* accept broadcast messages */
-#define SNDRV_SEQ_FILTER_MULTICAST	(1<<1)	/* accept multicast messages */
-#define SNDRV_SEQ_FILTER_BOUNCE		(1<<2)	/* accept bounce event in error */
-#define SNDRV_SEQ_FILTER_USE_EVENT	(1<<31)	/* use event filter */
+#define SNDRV_SEQ_FILTER_BROADCAST	(1U<<0)	/* accept broadcast messages */
+#define SNDRV_SEQ_FILTER_MULTICAST	(1U<<1)	/* accept multicast messages */
+#define SNDRV_SEQ_FILTER_BOUNCE		(1U<<2)	/* accept bounce event in error */
+#define SNDRV_SEQ_FILTER_USE_EVENT	(1U<<31)	/* use event filter */

 struct snd_seq_client_info {
 	int client;			/* client number to inquire */
-- 
2.25.1