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Thu, 4 Nov 2021 10:47:48 +0000 Date: Thu, 4 Nov 2021 13:47:27 +0300 From: Dan Carpenter To: George Kennedy Cc: gregkh@linuxfoundation.org, jejb@linux.ibm.com, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] scsi: scsi_debug: fix return checks for kcalloc Message-ID: <20211104104727.GA3164@kadam> References: <1635966102-29320-1-git-send-email-george.kennedy@oracle.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1635966102-29320-1-git-send-email-george.kennedy@oracle.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: JNXP275CA0016.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:19::28) To MWHPR1001MB2365.namprd10.prod.outlook.com (2603:10b6:301:2d::28) MIME-Version: 1.0 Received: from kadam (102.222.70.114) by JNXP275CA0016.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:19::28) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4669.10 via Frontend Transport; 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It has no effect on run time. On Wed, Nov 03, 2021 at 02:01:42PM -0500, George Kennedy wrote: > Change return checks from kcalloc() to now check for NULL and > ZERO_SIZE_PTR using the ZERO_OR_NULL_PTR macro or the following > crash can occur if ZERO_SIZE_PTR indicator is returned. ZERO_SIZE_PTR is when you allocate a zero bytes successfully. It's quite useful because you can do: p = kmalloc(bytes, GFP_KERNEL); for (i = 0; i < bytes; i++) printk("%d\n", p[i]); The for loop works. Zero bytes now like normal thing instead of needing to be handled as a special case. The IS_ERR_OR_NULL() check treats ZERO_SIZE_PTR as a valid pointer. > diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c > index 40b473e..222e985 100644 > --- a/drivers/scsi/scsi_debug.c > +++ b/drivers/scsi/scsi_debug.c > @@ -3909,7 +3909,7 @@ static int resp_comp_write(struct scsi_cmnd *scp, > return ret; > dnum = 2 * num; > arr = kcalloc(lb_size, dnum, GFP_ATOMIC); > - if (NULL == arr) { > + if (ZERO_OR_NULL_PTR(arr)) { kcalloc() only returns NULL on error. This check is Yoda code but besides the style issue it's fine. > mk_sense_buffer(scp, ILLEGAL_REQUEST, INSUFF_RES_ASC, > INSUFF_RES_ASCQ); > return check_condition_result; > @@ -4265,7 +4265,7 @@ static int resp_verify(struct scsi_cmnd *scp, struct sdebug_dev_info *devip) > return ret; > > arr = kcalloc(lb_size, vnum, GFP_ATOMIC); > - if (!arr) { The rest of these are correct. This patch doesn't fix a bug... regards, dan carpenter