linux-kernel - Re: [PATCH 6.12.y] mm/mmap: fix __mmap_region() error handling in rare merge failure case

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Message-ID: <4e10f9e9-11e7-4f02-88b7-47102197e93a@suse.cz>
Date: Tue, 19 Nov 2024 15:36:40 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Greg KH <gregkh@...uxfoundation.org>,
 Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Jann Horn <jannh@...gle.com>,
 syzbot+bc6bfc25a68b7a020ee1@...kaller.appspotmail.com, stable@...r.kernel.org
Subject: Re: [PATCH 6.12.y] mm/mmap: fix __mmap_region() error handling in
 rare merge failure case

On 11/19/24 15:25, Liam R. Howlett wrote:
> * Greg KH <gregkh@...uxfoundation.org> [241119 09:17]:
>> On Mon, Nov 18, 2024 at 03:32:14PM -0500, Liam R. Howlett wrote:
>> > Okay, before I get yelled at...
>> > 
>> > This commit is only necessary for 6.12.y until Lorenzo's other fixes to
>> > older stables land (and I'll have to figure out what to do in each).
>> > 
>> > The commit will not work on mm-unstable, because it doesn't exist due to
>> > refactoring.
>> > 
>> > The commit does not have a tag about "upstream commit" because there
>> > isn't one - the closest thing I could point to does not have a stable
>> > git id.
>> > 
>> > So here I am with a fix for a kernel that was released a few hours ago
>> > that is not necessary in v6.13, for a bug that's out there on syzkaller.
>> > 
>> > Also, it's very unlikely to happen unless you inject failures like
>> > syzkaller.  But hey, pretty decent turn-around on finding a fix - so
>> > that's a rosy outlook.
>> 
>> Why isn't this needed in 6.13.y?  What's going to be different in there
>> that this isn't needed?
> 
> The code has been refactored and avoids the scenario.  I'd name the
> refactoring commit as the upstream commit, but it does not have a stable
> git id as it's in mm-unstable.  So I'm at a bit of a loss of how to
> follow the process.

Is it not in mm-stable now, given we're in a merge window? Anyway AFAIU if
the stable-specific fix is completely different from the upstream
refactoring, we don't even try to pretend it's the same "commit XYZ
upstream" no?

>> 
>> Do you just want me to take this for the 6.12.y tree now?  I'll be glad
>> to, just confused a bit.
> 
> Yes, please.
> 
> 
> Thanks,
> Liam