linux-kernel - RE: [PATCH v4 3/5] scsi: ufs: fix potential access NULL pointer while memcpy

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Message-ID: <SN6PR04MB4640741E1DC89A927F8A60A5FC8A0@SN6PR04MB4640.namprd04.prod.outlook.com>
Date:   Mon, 1 Jun 2020 06:25:12 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Bean Huo <huobean@...il.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "tomas.winkler@...el.com" <tomas.winkler@...el.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4 3/5] scsi: ufs: fix potential access NULL pointer while
 memcpy

Hi,

> If param_offset is not 0, the memcpy length shouldn't be the
> true descriptor length.
> 
> Fixes: a4b0e8a4e92b ("scsi: ufs: Factor out ufshcd_read_desc_param")
> Signed-off-by: Bean Huo <beanhuo@...ron.com>
> ---
>  drivers/scsi/ufs/ufshcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index f7e8bfefe3d4..bc52a0e89cd3 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -3211,7 +3211,7 @@ int ufshcd_read_desc_param(struct ufs_hba *hba,
> 
>         /* Check wherher we will not copy more data, than available */
>         if (is_kmalloc && param_size > buff_len)
> -               param_size = buff_len;
> +               param_size = buff_len - param_offset;
But Is_kmalloc is true if (param_offset != 0 || param_size < buff_len)
So  if (is_kmalloc && param_size > buff_len) implies that param_offset is 0,
Or did I get it wrong?

Still, I think that there is a problem here because nowhere we are checking that  
param_offset + param_size < buff_len, which now can happen because of ufs-bsg.

Maybe you can add it and get rid of that is_kmalloc which is an awkward way to test for valid values?

Thanks,
Avri
> 
>         if (is_kmalloc)
>                 memcpy(param_read_buf, &desc_buf[param_offset], param_size);
> --
> 2.17.1