Re: [PATCH v2 5.10/5.15] ata: libata-scsi: check cdb length for VARIABLE_LENGTH_CMD commands

[Damien Le Moal]

On 4/11/24 19:30, Mikhail Ukhin wrote:
> No upstream commit exists for this patch.
> 
> Fuzzing of 5.10 stable branch reports a slab-out-of-bounds error in
> ata_scsi_pass_thru.
> 
> The error is fixed in 5.18 by commit ce70fd9a551a ("scsi: core: Remove the
> cmd field from struct scsi_request") upstream.
> Backporting this commit would require significant changes to the code so
> it is bettter to use a simple fix for that particular error.
> 
> The problem is that the length of the received SCSI command is not
> validated if scsi_op == VARIABLE_LENGTH_CMD. It can lead to out-of-bounds
> reading if the user sends a request with SCSI command of length less than
> 32.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
> 
> Signed-off-by: Artem Sadovnikov <ancowi69@xxxxxxxxx>
> Signed-off-by: Mikhail Ivanov <iwanov-23@xxxxx>
> Signed-off-by: Mikhail Ukhin <mish.uxin2012@xxxxxxxxx>
> ---
>  v2: The new addresses were added and the text was updated. 
>  drivers/ata/libata-scsi.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index dfa090ccd21c..77589e911d3d 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -4065,6 +4065,9 @@ int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
>  
>  	if (unlikely(!scmd->cmd_len))
>  		goto bad_cdb_len;
> +
> +	if (scsi_op == VARIABLE_LENGTH_CMD && scmd->cmd_len < 32)
> +		goto bad_cdb_len;

This check should really be in ata_scsi_var_len_cdb_xlat(). Please move it to
that function.

>  
>  	if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
>  		if (unlikely(scmd->cmd_len > dev->cdb_len))

-- 
Damien Le Moal
Western Digital Research