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

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Message-ID: <aLBn4vb0Pmwoqt51@google.com>
Date: Thu, 28 Aug 2025 14:29:54 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Vlastimil Babka <vbabka@...e.cz>,
	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 03:22:54PM +0100, Lorenzo Stoakes wrote:
> 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 :)

Oops, sorry my v2 raced with this.