From: "Harry Yoo (Oracle)" <harry@kernel.org>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Brendan Jackman <jackmanb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>, Zi Yan <ziy@nvidia.com>,
Shakeel Butt <shakeel.butt@linux.dev>,
Alexei Starovoitov <ast@kernel.org>, Hao Li <hao.li@linux.dev>,
Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH mm-hotfixes v2 0/2] mm/page_alloc,slab: return NULL early from *_nolock() memory allocation APIs in NMI on UP
Date: Mon, 27 Apr 2026 17:13:22 +0900 [thread overview]
Message-ID: <ae8aojxbv4PHq_C3@desktop.tail10959e.ts.net> (raw)
In-Reply-To: <c3f7b8e4-85ae-4e80-bb02-a7b205cec88e@kernel.org>
On Mon, Apr 27, 2026 at 10:00:16AM +0200, Vlastimil Babka (SUSE) wrote:
> On 4/27/26 09:09, Harry Yoo (Oracle) wrote:
> > Due to my mistake, V1 was sent twice w/o proper cover letter and
> > Cc: stable. Please ignore V1. Apologies for the noise.
> >
> > Changes since V1:
> > - used b4 to send patch series (w/ a proper cover letter) instead of
> > my broken git send-email script (Thanks Vlastimil)
> > - added Cc: stable to patches 1 and 2
> >
> > On UP kernels (!CONFIG_SMP), spin_trylock() is a no-op that
> > unconditionally succeeds even when the lock is already held.
> > As a result, alloc_frozen_pages_nolock() and kmalloc_nolock() called
> > from an NMI context can successfully re-acquire the lock that the
> > page/slab allocators are already holding (no deadlock because it's
> > trylock, but leads to e.g., allocating the same page/object twice and
> > causing use-after-free).
> >
> > It was discovered while testing the new kmalloc/kfree_nolock() test case
> > in the slub_kunit test module with CONFIG_DEBUG_SPINLOCK=y on a UP
> > kernel.
> >
> > Patch 1 fixes alloc_frozen_pages_nolock() and
> > patch 2 fixes kmalloc_nolock().
>
> Thanks. Given the problem exposed is in a slab kunit test I think it's
> better to handle this in the slab tree.
Ack, I'm fine either way.
> The page_alloc change is small and
> should not cause conflicts.
Right.
> So I've merged both in slab/for-next.
Thanks! (I see it's been added to slab/for-next-fixes)
--
Cheers,
Harry / Hyeonggon
prev parent reply other threads:[~2026-04-27 8:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-27 7:09 [PATCH mm-hotfixes v2 0/2] mm/page_alloc,slab: return NULL early from *_nolock() memory allocation APIs in NMI on UP Harry Yoo (Oracle)
2026-04-27 7:09 ` [PATCH mm-hotfixes v2 1/2] mm/page_alloc: return NULL early from alloc_frozen_pages_nolock() " Harry Yoo (Oracle)
2026-04-27 7:09 ` [PATCH mm-hotfixes v2 2/2] mm/slab: return NULL early from kmalloc_nolock() " Harry Yoo (Oracle)
2026-04-27 8:00 ` [PATCH mm-hotfixes v2 0/2] mm/page_alloc,slab: return NULL early from *_nolock() memory allocation APIs " Vlastimil Babka (SUSE)
2026-04-27 8:13 ` Harry Yoo (Oracle) [this message]
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