linux-kernel - Re: [PATCH][next] scsi: sg: Fix use of pointer sfp after it has been kfree'd

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Date:   Thu, 11 Mar 2021 12:17:30 -0500
From:   Douglas Gilbert <dgilbert@...erlog.com>
To:     Colin King <colin.king@...onical.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Hannes Reinecke <hare@...e.de>, linux-scsi@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] scsi: sg: Fix use of pointer sfp after it has been
 kfree'd

On 2021-03-11 5:37 a.m., Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently SG_LOG is referencing sfp after it has been kfree'd which
> is probably a bad thing to do. Fix this by kfree'ing sfp after
> SG_LOG.
> 
> Addresses-Coverity: ("Use after free")
> Fixes: af1fc95db445 ("scsi: sg: Replace rq array with xarray")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Acked-by: Douglas Gilbert <dgilbert@...erlog.com>

Thanks.

> ---
>   drivers/scsi/sg.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 2d4bbc1a1727..79f05afa4407 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -3799,10 +3799,10 @@ sg_add_sfp(struct sg_device *sdp)
>   	if (rbuf_len > 0) {
>   		srp = sg_build_reserve(sfp, rbuf_len);
>   		if (IS_ERR(srp)) {
> -			kfree(sfp);
>   			err = PTR_ERR(srp);
>   			SG_LOG(1, sfp, "%s: build reserve err=%ld\n", __func__,
>   			       -err);
> +			kfree(sfp);
>   			return ERR_PTR(err);
>   		}
>   		if (srp->sgat_h.buflen < rbuf_len) {
>