linux-kernel - Re: [PATCH] mm/util: make memdup_user_nul() similar to memdup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20241223172552.133f4e293f1dfbb6aa86b5ef@linux-foundation.org>
Date: Mon, 23 Dec 2024 17:25:52 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/util: make memdup_user_nul() similar to
 memdup_user()

tl;dr: patch does three different things, some of which appear to be
needed in -stable kernels.

On Sat, 21 Dec 2024 16:47:29 +0900 Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> wrote:

> Since the string data to copy from userspace is likely less than PAGE_SIZE
> bytes, replace GFP_KERNEL with GFP_USER like commit 6c2c97a24f09
> ("memdup_user(): switch to GFP_USER") does

Please provide a reason for this change.  Does it have user-visible
effects?  If so, what are they?

> and add __GFP_NOWARN like commit
> 6c8fcc096be9 ("mm: don't let userspace spam allocations warnings") does.

Ditto.

> Also, use dedicated slab buckets like commit d73778e4b867 ("mm/util: Use
> dedicated slab buckets for memdup_user()") does.

Ditto.

> Reported-by: syzbot+7e12e97b36154c54414b@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=7e12e97b36154c54414b

That's a userspace-triggered WARN, so we'll want to backport the fix
into -stable kernels.  But we won't necessarly want to backport the
other two changes, depending upon what their effects are.

In other words, it would be better to present this as a series of three
(fully changelogged!) patches, with one or more of them cc:stable.

If we really do want to roll all three changes into a single patch and
backport that then please let's justify all three backports within the
changelog.