[PATCH] rawmidi: virtual: fix reading into a small buffer

[PATCH] rawmidi: virtual: fix reading into a small buffer

[Clemens Ladisch]

In the special case for handling partial messages, the pointer
calculations were wrong, which would result in data corruption.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

--- alsa-lib/src/rawmidi/rawmidi_virt.c
+++ alsa-lib/src/rawmidi/rawmidi_virt.c
@@ -263,8 +263,8 @@ static ssize_t snd_rawmidi_virtual_read(snd_rawmidi_t *rmidi, void *buffer, size
 		}
 		size1 = virt->in_buf_size - virt->in_buf_ofs;
 		if ((size_t)size1 > size) {
-			virt->in_buf_ofs += size1 - size;
-			memcpy(buffer, virt->in_buf_ptr, size);
+			memcpy(buffer, virt->in_buf_ptr + virt->in_buf_ofs, size);
+			virt->in_buf_ofs += size;
 			result += size;
 			break;
 		}

Re: [PATCH] rawmidi: virtual: fix reading into a small buffer

[Takashi Sakamoto]

Hi,

On Mar 19 2017 07:10, Clemens Ladisch wrote:
> In the special case for handling partial messages, the pointer
> calculations were wrong, which would result in data corruption.
>
> Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

Reviewd-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

> --- alsa-lib/src/rawmidi/rawmidi_virt.c
> +++ alsa-lib/src/rawmidi/rawmidi_virt.c
> @@ -263,8 +263,8 @@ static ssize_t snd_rawmidi_virtual_read(snd_rawmidi_t *rmidi, void *buffer, size
>  		}
>  		size1 = virt->in_buf_size - virt->in_buf_ofs;
>  		if ((size_t)size1 > size) {
> -			virt->in_buf_ofs += size1 - size;
> -			memcpy(buffer, virt->in_buf_ptr, size);
> +			memcpy(buffer, virt->in_buf_ptr + virt->in_buf_ofs, size);
> +			virt->in_buf_ofs += size;
>  			result += size;
>  			break;
>  		}


Regards

Takashi Sakamoto

Re: [PATCH] rawmidi: virtual: fix reading into a small buffer

[Takashi Iwai]

On Sat, 18 Mar 2017 23:10:33 +0100,
Clemens Ladisch wrote:
> 
> In the special case for handling partial messages, the pointer
> calculations were wrong, which would result in data corruption.
> 
> Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

Applied (with Sakamoto-san's review tag) now.  Thanks.


Takashi

> 
> --- alsa-lib/src/rawmidi/rawmidi_virt.c
> +++ alsa-lib/src/rawmidi/rawmidi_virt.c
> @@ -263,8 +263,8 @@ static ssize_t snd_rawmidi_virtual_read(snd_rawmidi_t *rmidi, void *buffer, size
>  		}
>  		size1 = virt->in_buf_size - virt->in_buf_ofs;
>  		if ((size_t)size1 > size) {
> -			virt->in_buf_ofs += size1 - size;
> -			memcpy(buffer, virt->in_buf_ptr, size);
> +			memcpy(buffer, virt->in_buf_ptr + virt->in_buf_ofs, size);
> +			virt->in_buf_ofs += size;
>  			result += size;
>  			break;
>  		}
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