2022-11-21 05:05:00

by Baisong Zhong

Subject: [PATCH -next] 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]>
---
include/uapi/sound/asequencer.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/sound/asequencer.h b/include/uapi/sound/asequencer.h
index 6d4a2c60808d..4c5c4dd15d02 100644
--- a/include/uapi/sound/asequencer.h
+++ b/include/uapi/sound/asequencer.h
@@ -331,7 +331,7 @@ typedef int __bitwise snd_seq_client_type_t;
#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_USE_EVENT (1U<<31) /* use event filter */

struct snd_seq_client_info {
int client; /* client number to inquire */
--
2.17.1

2022-11-21 10:38:20

by Takashi Iwai

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

On Mon, 21 Nov 2022 05:36:25 +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]>
> ---
> include/uapi/sound/asequencer.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/uapi/sound/asequencer.h b/include/uapi/sound/asequencer.h
> index 6d4a2c60808d..4c5c4dd15d02 100644
> --- a/include/uapi/sound/asequencer.h
> +++ b/include/uapi/sound/asequencer.h
> @@ -331,7 +331,7 @@ typedef int __bitwise snd_seq_client_type_t;
> #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_USE_EVENT (1U<<31) /* use event filter */

Similarly like the previous patch for PCM, could you update all
SNDRV_SEQ_FILTER_* to 1U for consistency?


thanks,

Takashi

2022-11-21 11:04:11

by Baisong Zhong

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

在 2022/11/21 18:35, Takashi Iwai 写道:
> On Mon, 21 Nov 2022 05:36:25 +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]>
>> ---
>> include/uapi/sound/asequencer.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/uapi/sound/asequencer.h b/include/uapi/sound/asequencer.h
>> index 6d4a2c60808d..4c5c4dd15d02 100644
>> --- a/include/uapi/sound/asequencer.h
>> +++ b/include/uapi/sound/asequencer.h
>> @@ -331,7 +331,7 @@ typedef int __bitwise snd_seq_client_type_t;
>> #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_USE_EVENT (1U<<31) /* use event filter */
>
> Similarly like the previous patch for PCM, could you update all
> SNDRV_SEQ_FILTER_* to 1U for consistency?
>
>
> thanks,
>
> Takashi

Hi, Takashi
Thank you for your suggestion. I will update all
SNDRV_SEQ_FILTER_* to 1U for consistency in v2.

Baisong Zhong
.