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

[Takashi Iwai]

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 <zhongbaisong@xxxxxxxxxx>
> ---
> v2: update all SNDRV_SEQ_FILTER_* to 1U to keep consistent

Thanks, applied now.


Takashi