Re: [PATCH] scsi: megasas: Internal cdbs have 16-byte length

[Fiona Ebner]

Am 28.02.23 um 18:11 schrieb Guenter Roeck:
> Host drivers do not necessarily set cdb_len in megasas io commands.
> With commits 6d1511cea0 ("scsi: Reject commands if the CDB length
> exceeds buf_len") and fe9d8927e2 ("scsi: Add buf_len parameter to
> scsi_req_new()"), this results in failures to boot Linux from affected
> SCSI drives because cdb_len is set to 0 by the host driver.
> Set the cdb length to its actual size to solve the problem.
> 

Tested-by: Fiona Ebner <f.ebner@proxmox.com>

But I do have a question:

> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  hw/scsi/megasas.c | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/hw/scsi/megasas.c b/hw/scsi/megasas.c
> index 9cbbb16121..d624866bb6 100644
> --- a/hw/scsi/megasas.c
> +++ b/hw/scsi/megasas.c
> @@ -1780,7 +1780,7 @@ static int megasas_handle_io(MegasasState *s, 
> MegasasCmd *cmd, int frame_cmd)
>      uint8_t cdb[16];
>      int len;
>      struct SCSIDevice *sdev = NULL;
> -    int target_id, lun_id, cdb_len;
> +    int target_id, lun_id;
>  
>      lba_count = le32_to_cpu(cmd->frame->io.header.data_len);
>      lba_start_lo = le32_to_cpu(cmd->frame->io.lba_lo);
> @@ -1789,7 +1789,6 @@ static int megasas_handle_io(MegasasState *s, 
> MegasasCmd *cmd, int frame_cmd)
>  
>      target_id = cmd->frame->header.target_id;
>      lun_id = cmd->frame->header.lun_id;
> -    cdb_len = cmd->frame->header.cdb_len;
>  
>      if (target_id < MFI_MAX_LD && lun_id == 0) {
>          sdev = scsi_device_find(&s->bus, 0, target_id, lun_id);
> @@ -1804,15 +1803,6 @@ static int megasas_handle_io(MegasasState *s, 
> MegasasCmd *cmd, int frame_cmd)
>          return MFI_STAT_DEVICE_NOT_FOUND;
>      }
>  
> -    if (cdb_len > 16) {
> -        trace_megasas_scsi_invalid_cdb_len(
> -            mfi_frame_desc(frame_cmd), 1, target_id, lun_id, cdb_len);
> -        megasas_write_sense(cmd, SENSE_CODE(INVALID_OPCODE));
> -        cmd->frame->header.scsi_status = CHECK_CONDITION;
> -        s->event_count++;
> -        return MFI_STAT_SCSI_DONE_WITH_ERROR;
> -    }

Shouldn't we still fail when cmd->frame->header.cdb_len > 16? Or is the
consequence of

> Host drivers do not necessarily set cdb_len in megasas io commands.

that this can be uninitialized memory and we need to assume it was not
explicitly set?

Best Regards,
Fiona

> -
>      cmd->iov_size = lba_count * sdev->blocksize;
>      if (megasas_map_sgl(s, cmd, &cmd->frame->io.sgl)) {
>          megasas_write_sense(cmd, SENSE_CODE(TARGET_FAILURE));
> @@ -1823,7 +1813,7 @@ static int megasas_handle_io(MegasasState *s, 
> MegasasCmd *cmd, int frame_cmd)
>  
>      megasas_encode_lba(cdb, lba_start, lba_count, is_write);
>      cmd->req = scsi_req_new(sdev, cmd->index,
> -                            lun_id, cdb, cdb_len, cmd);
> +                            lun_id, cdb, sizeof(cdb), cmd);
>      if (!cmd->req) {
>          trace_megasas_scsi_req_alloc_failed(
>              mfi_frame_desc(frame_cmd), target_id, lun_id);