linux-kernel - Re: [PATCH 1/2] btrfs: Prevent open-coded arithmetic in kmalloc

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Message-ID: <20250923061344.GT5333@twin.jikos.cz>
Date: Tue, 23 Sep 2025 08:13:44 +0200
From: David Sterba <dsterba@...e.cz>
To: Miquel Sabaté Solà <mssola@...ola.com>
Cc: David Sterba <dsterba@...e.cz>, linux-btrfs@...r.kernel.org, clm@...com,
	dsterba@...e.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] btrfs: Prevent open-coded arithmetic in kmalloc

On Mon, Sep 22, 2025 at 02:47:13PM +0200, Miquel Sabaté Solà wrote:
> Hello,
> 
> David Sterba @ 2025-09-22 12:28 +02:
> 
> > On Fri, Sep 19, 2025 at 04:58:15PM +0200, Miquel Sabaté Solà wrote:
> >> As pointed out in the documentation, calling 'kmalloc' with open-coded
> >> arithmetic can lead to unfortunate overflows and this particular way of
> >> using it has been deprecated. Instead, it's preferred to use
> >> 'kmalloc_array' in cases where it might apply so an overflow check is
> >> performed.
> >
> > So this is an API cleanup and it makes sense to use the checked
> > multiplication but it should be also said that this is not fixing any
> > overflow because in all cases the multipliers are bounded small numbers
> > derived from number of items in leaves/nodes.
> 
> Yes, it's just an API cleanup and I don't think it fixes any current bug
> in the code base. So no need to CC stable or anything like that.

Still the changelog should say explicitly that it's not a bug fix before
somebody assigns a CVE to it because it mentions overflow.