2022-11-21 12:20:37

by Baisong Zhong

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 <[email protected]>
---
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

2022-11-23 07:28:39

by Takashi Iwai

Subject: Re: [PATCH -next v2] ALSA: seq: fix undefined behavior in bit shift for SNDRV_SEQ_FILTER_USE_EVENT

On Mon, 21 Nov 2022 12:16:30 +0100,
Baisong Zhong wrote:
>
> 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 <[email protected]>
> ---
> v2: update all SNDRV_SEQ_FILTER_* to 1U to keep consistent

Thanks, applied now.


Takashi