linux-kernel - Re: [PATCH] mm/mremap: fix regression in vrm->new

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Message-ID: <b58449cc-022b-497a-97f2-c91776d133dc@lucifer.local>
Date: Thu, 28 Aug 2025 15:22:54 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Carlos Llamas <cmllamas@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org,
        "open list:MEMORY MAPPING" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm/mremap: fix regression in vrm->new_addr check

On Thu, Aug 28, 2025 at 04:21:05PM +0200, Vlastimil Babka wrote:
> On 8/28/25 07:38, Lorenzo Stoakes wrote:
> > On Thu, Aug 28, 2025 at 03:26:52AM +0000, Carlos Llamas wrote:
> >> Commit 3215eaceca87 ("mm/mremap: refactor initial parameter sanity
> >> checks") moved the sanity check for vrm->new_addr from mremap_to() to
> >> check_mremap_params().
> >>
> >> However, this caused a regression as vrm->new_addr is now checked even
> >> when MREMAP_FIXED and MREMAP_DONTUNMAP flags are not specified. In this
> >> case, vrm->new_addr can be garbage and create unexpected failures.
> >
> > Yikes, sorry my mistake.
> >
> >>
> >> Fix this by moving the new_addr check after the vrm_implies_new_addr()
> >> guard. This ensures that the new_addr is only checked when the user has
> >> specified one explicitly.
> >>
> >> Fixes: 3215eaceca87 ("mm/mremap: refactor initial parameter sanity checks")
> >> Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
> >
> > You need a Cc: Stable.
>
> No need as the commit being fixed is from 6.17-rc1?
> But it's better to use "[PATCH mm-hotfixes]" to make sure it goes to 6.17
> and not the next merge window.
>

Ah haha really? I'm losing track of my patches.

Yeah sure as per Vlasta then Carlos :)