linux-kernel - Re: [PATCH 28/44] drivers/usb/storage: use min() instead of min

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <4208129f-a768-44e2-843f-309c50ea362f@rowland.harvard.edu>
Date: Wed, 19 Nov 2025 21:59:42 -0500
From: Alan Stern <stern@...land.harvard.edu>
To: david.laight.linux@...il.com
Cc: linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	usb-storage@...ts.one-eyed-alien.net,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 28/44] drivers/usb/storage: use min() instead of min_t()

On Wed, Nov 19, 2025 at 10:41:24PM +0000, david.laight.linux@...il.com wrote:
> From: David Laight <david.laight.linux@...il.com>
> 
> min_t(unsigned int, a, b) casts an 'unsigned long' to 'unsigned int'.
> Use min(a, b) instead as it promotes any 'unsigned int' to 'unsigned long'
> and so cannot discard significant bits.
> 
> In this case the 'unsigned long' value is small enough that the result
> is ok.
> 
> Detected by an extra check added to min_t().

In fact, min_t(T, a, b) cannot go wrong as long as all the types are 
unsigned and at least one of a, b has type T or smaller.  Of course, in 
this situation there's no reason not to simply use min().  (And if both 
a and b have types larger than T, why would someone use min_t() like 
this in the first place?)

Regardless, the patch is fine with me.

Acked-by: Alan Stern <stern@...land.harvard.edu>

Alan Stern

> Signed-off-by: David Laight <david.laight.linux@...il.com>
> ---
>  drivers/usb/storage/protocol.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c
> index 9033e505db7f..0cff54ad90fa 100644
> --- a/drivers/usb/storage/protocol.c
> +++ b/drivers/usb/storage/protocol.c
> @@ -139,8 +139,7 @@ unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
>  		return cnt;
>  
>  	while (sg_miter_next(&miter) && cnt < buflen) {
> -		unsigned int len = min_t(unsigned int, miter.length,
> -				buflen - cnt);
> +		unsigned int len = min(miter.length, buflen - cnt);
>  
>  		if (dir == FROM_XFER_BUF)
>  			memcpy(buffer + cnt, miter.addr, len);
> -- 
> 2.39.5
>