[dm-devel] multipath-tools: mismatch between CDB allocation length and SG_IO dxfer_len

[Sebastian Herbszt]

> Hello,
> 
> while playing with multipath-tools and scst I got the following warning:
> 
> [ 6382.467569] [3806]: scst: scst_parse_cmd:826:Warning: expected
> transfer length 256 for opcode 0x12 (handler vdisk_blockio, target
> scst_local) doesn't match decoded value 128
> [ 6382.467574] [3806]: scst_parse_cmd:828:Suspicious CDB:
> [ 6382.467579]  (h)___0__1__2__3__4__5__6__7__8__9__A__B__C__D__E__F
> [ 6382.467581]    0: 12 01 c0 00 80 00   ......
> 
> This happened when my scst target pretended to be a CLARiiON.
> I noticed a mismatch in emc_clariion_prio (libmultipath/prioritizers/emc.c)
> between the allocation length and dxfer_len:
> 
> int emc_clariion_prio(const char *dev, int fd)
> {
>         unsigned char sense_buffer[256];
>         unsigned char sb[128];
>         unsigned char inqCmdBlk[INQUIRY_CMDLEN] = {INQUIRY_CMD, 1, 0xC0, 0,
>                                                 sizeof(sb), 0};
> 
> ...
> 
>         memset(&sense_buffer, 0, 256);
>         io_hdr.interface_id = 'S';
>         io_hdr.cmd_len = sizeof (inqCmdBlk);
>         io_hdr.mx_sb_len = sizeof (sb);
>         io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
>         io_hdr.dxfer_len = sizeof (sense_buffer);
>         io_hdr.dxferp = sense_buffer;
>         io_hdr.cmdp = inqCmdBlk;
>         io_hdr.sbp = sb;
>         io_hdr.timeout = 60000;
>         io_hdr.pack_id = 0;
> 
> The following change shrinks the size of sense_buffer to 128.
> 
> Sebastian
> 
> diff --git a/libmultipath/prioritizers/emc.c b/libmultipath/prioritizers/emc.c
> index 87e9a8d..91b3d90 100644
> --- a/libmultipath/prioritizers/emc.c
> +++ b/libmultipath/prioritizers/emc.c
> @@ -14,15 +14,15 @@
>  
>  int emc_clariion_prio(const char *dev, int fd)
>  {
> -	unsigned char sense_buffer[256];
> +	unsigned char sense_buffer[128];
>  	unsigned char sb[128];
>  	unsigned char inqCmdBlk[INQUIRY_CMDLEN] = {INQUIRY_CMD, 1, 0xC0, 0,
> -						sizeof(sb), 0};
> +						sizeof(sense_buffer), 0};
>  	struct sg_io_hdr io_hdr;
>  	int ret = PRIO_UNDEF;
>  
>  	memset(&io_hdr, 0, sizeof (struct sg_io_hdr));
> -	memset(&sense_buffer, 0, 256);
> +	memset(&sense_buffer, 0, 128);
>  	io_hdr.interface_id = 'S';
>  	io_hdr.cmd_len = sizeof (inqCmdBlk);
>  	io_hdr.mx_sb_len = sizeof (sb);

Ping! Any comments?

Sebastian