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b=seMxTGJN4uv6l+RdFXYx1uMxe4oufBuf9DmTpU6mefMKEkq+nUS6OyD2tYH7tZSaL 1vn27hcMwt7dXLXkBuElGqXmIzggyVJ6sdLXMnWiu/H6CE12CIjmUjzrmx0LtbjQmq jI6yj6Ssost+fkqK/jzHRdUeyG6QZSTsWSohW5PyHVuHQpq0FKcSd41j00KlT+FWcx 7D24Iw8X+d33WTN9Fe0+BYDDpEp6Ouhn65cgeU/Q5uwPqJWAyTZOyvwtNEGazy6MAN YUhOGaOVGw+W5rh4DGRABMMv/aiCeR4u9gTptrIF/+5l5aKNyptCW21EF6AMac48Yd 6hRJnhdAu3tGQ== Date: Mon, 27 Apr 2026 17:13:22 +0900 From: "Harry Yoo (Oracle)" To: "Vlastimil Babka (SUSE)" Cc: Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Shakeel Butt , Alexei Starovoitov , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , 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 Message-ID: References: <20260427-nolock-api-fix-v2-0-a6b83a92d9a4@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 19E081A000C X-Stat-Signature: h5a1ij5nwmz7a7nbc9bidmt69uarkxz5 X-Rspam-User: X-HE-Tag: 1777277605-57924 X-HE-Meta: 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 WsrMcbur MnEGhJW/0k2zNpAYs45xA4EOSC8qt1ztwzc3hMERwBKTypapWJw2aJ8ODBgzjFx2u/xdfhtGwEprPDms/5fnAfU63xSloM81/73ThZmbOZhP22gos6lULLlBh3HFpWm5IkvFzRKNQgVd89Ypa+eRK3GrYvS8FphxaYxcuyPSQD82au/ska358GaVGi5HOsfWqrY6+4ch0UIEOwISxVPfwUDPdcr0GjSt9kO6mL/8D45m6sRvDBBhy9KSc+7rtApwS+OCjLMwJ1/vJpbo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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