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

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Message-ID: <20250923070045.GU5333@twin.jikos.cz>
Date: Tue, 23 Sep 2025 09:00:46 +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 Tue, Sep 23, 2025 at 08:47:35AM +0200, Miquel Sabaté Solà wrote:
> David Sterba @ 2025-09-23 08:13 +02:
> 
> > 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.
> 
> Got it! I will submit a v2 and make this more explicit.

No need to, I've updated the changelog at commit time.