Re: [PATCH v5 5.10/5.15] ata: libata-scsi: check cdb length for VARIABLE_LENGTH_CMD commands

[Damien Le Moal <dlemoal@kernel.org>]

On 7/12/24 00:15, Artem Sadovnikov wrote:
> 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.
> 
> 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@gmail.com>
> Signed-off-by: Mikhail Ivanov <iwanov-23@bk.ru>
> Signed-off-by: Mikhail Ukhin <mish.uxin2012@yandex.ru>

Looks good, so please feel free to add:

Acked-by: Damien Le Moal <dlemoal@kernel.org>

However, you did not address this patch to linux-stable and Greg, so it will go
nowhere as is since I cannot apply that to stable. So please check:

Documentation/process/stable-kernel-rules.rst

and see "option 2".

> ---
>  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 36f32fa052df..4397986db053 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3949,6 +3949,9 @@ static unsigned int ata_scsi_var_len_cdb_xlat(struct ata_queued_cmd *qc)
>  	const u8 *cdb = scmd->cmnd;
>  	const u16 sa = get_unaligned_be16(&cdb[8]);
>  
> +	if (scmd->cmd_len != 32)
> +		return 1;
> +
>  	/*
>  	 * if service action represents a ata pass-thru(32) command,
>  	 * then pass it to ata_scsi_pass_thru handler.

-- 
Damien Le Moal
Western Digital Research