linux-kernel - Re: [dm-devel] [PATCH] md: dm-ioctl: drop always-false condition

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Message-ID: <alpine.LRH.2.21.2301180658250.13031@file01.intranet.prod.int.rdu2.redhat.com>
Date:   Wed, 18 Jan 2023 06:59:02 -0500 (EST)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Sergey Shtylyov <s.shtylyov@....ru>
cc:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com,
        lvc-patches@...uxtesting.org, linux-kernel@...r.kernel.org
Subject: Re: [dm-devel] [PATCH] md: dm-ioctl: drop always-false condition

On Tue, 17 Jan 2023, Sergey Shtylyov wrote:

> The expression 'indata[3] > ULONG_MAX' always evaluates to false since
> indata[] is declared as an array of *unsigned long* elements and #define
> ULONG_MAX represents the max value of that exact type...
> 
> Note that gcc seems to be able to detect the dead code here and eliminate
> this check anyway...
> 
> Found by Linux Verification Center (linuxtesting.org) with the SVACE static
> analysis tool.
> 
> Signed-off-by: Sergey Shtylyov <s.shtylyov@....ru>

Reviewed-by: Mikulas Patocka <mpatocka@...hat.com>

> ---
> This patch is atop of the 'for-next' branch of the device-mapper repo...
> 
>  drivers/md/dm-ioctl.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> Index: linux-dm/drivers/md/dm-ioctl.c
> ===================================================================
> --- linux-dm.orig/drivers/md/dm-ioctl.c
> +++ linux-dm/drivers/md/dm-ioctl.c
> @@ -1073,8 +1073,7 @@ static int dev_set_geometry(struct file
>  		goto out;
>  	}
>  
> -	if (indata[0] > 65535 || indata[1] > 255 ||
> -	    indata[2] > 255 || indata[3] > ULONG_MAX) {
> +	if (indata[0] > 65535 || indata[1] > 255 || indata[2] > 255) {
>  		DMERR("Geometry exceeds range limits.");
>  		goto out;
>  	}
> 
> --
> dm-devel mailing list
> dm-devel@...hat.com
> https://listman.redhat.com/mailman/listinfo/dm-devel
> 

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