From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D9CD3223708 for ; Mon, 27 Apr 2026 05:42:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777268531; cv=none; b=eoiHD5UPdwDBd/KY8N8gjiwmGYOmGAVvilOCkJ+rH5hwUkbJh7I52KexBIqDjPhcXybkq7YS6AizgFvHe35Uj7Bl/15FANbI3cti2lSxoqsXvClEektsHI66UjUK74FwaGRCTIVi2aI5K/YWCae0YVu0TAak1OqE55E4UKZcfAg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777268531; c=relaxed/simple; bh=iipSs6v6w0TU4vM721+EG7SCFN/Hickx4k4+AOF1ykw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UMskdmfGvwplllIyS0P1sDWmxdtiaqtpnhQvZ3/B+no2UEU9GuSrxN25vj07+zbEINoYN2qS13LYczOFFS70vdUErQrB6M7nAnS5lE7GKciZ5F4s8phjKJAidSkgWFlEiJLhUr5lAcA5g8wo9Vqfrqg59gLHQvx/lTKlt6J+hds= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EknsdmMD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EknsdmMD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F142EC19425; Mon, 27 Apr 2026 05:42:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777268531; bh=iipSs6v6w0TU4vM721+EG7SCFN/Hickx4k4+AOF1ykw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EknsdmMD/enifxH8VPV8H+qG6cwpocmLVCoiW7B+3U7CZljO4P8/YYBWxa1/ROzU8 5ciro/zNJL6+1Ekw1qf5xfG3uc+nh7aJzzgL/TZKhuVnl5kks9BGc5lwmNq5ViRa/w Bf/uZ/gLam1vEH2k5RbicgvTK8CYkGZbyM7chBtwS0Qllmx/Q8HRc3P2RLDvo1t+zH 7Bn6D1RYgkGkRiD6Cvf8RBbVr8vT32IWvqi/NN/jFvut9fFUm+lBC67M2oAFHZNkmh 8LO/IZzH/MFsYY1f/VGTRljSoMJ7Qs5tz5eRiHKLMDLhjE/Nj7H1rIobveui/U+LyO 5elLbmHn4l2gw== From: "Harry Yoo (Oracle)" To: Andrew Morton , Vlastimil Babka , Shakeel Butt , Alexei Starovoitov , Harry Yoo Cc: Harry Yoo , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH mm-hotfixes 1/2] mm/page_alloc: return NULL early from alloc_frozen_pages_nolock() in NMI on UP Date: Mon, 27 Apr 2026 14:42:03 +0900 Message-ID: <20260427054205.560734-2-harry@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260427054205.560734-1-harry@kernel.org> References: <20260427054205.560734-1-harry@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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() called from NMI context can re-enter rmqueue() and acquire the zone lock that the interrupted context is already holding, corrupting the freelists. With CONFIG_DEBUG_SPINLOCK on UP, the following BUG is triggered with the slub_kunit test module: BUG: spinlock trylock failure on UP on CPU#0, kunit_try_catch/243 [...] Call Trace: dump_stack_lvl+0x3f/0x60 do_raw_spin_trylock+0x41/0x50 _raw_spin_trylock+0x24/0x50 rmqueue.isra.0+0x2a9/0xa70 get_page_from_freelist+0xeb/0x450 alloc_frozen_pages_nolock_noprof+0x111/0x1e0 allocate_slab+0x42a/0x500 ___slab_alloc+0xa7/0x4c0 kmalloc_nolock_noprof+0x164/0x310 [...] Fix this by returning NULL early when invoked from NMI on a UP kernel. Link: https://lore.kernel.org/linux-mm/ad_cqe51pvr1WaDg@hyeyoo Fixes: d7242af86434 ("mm: Introduce alloc_frozen_pages_nolock()") Signed-off-by: Harry Yoo (Oracle) --- mm/page_alloc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 71859993dd54..23c7298d3be2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7737,6 +7737,11 @@ struct page *alloc_frozen_pages_nolock_noprof(gfp_t gfp_flags, int nid, unsigned */ if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) return NULL; + + /* On UP, spin_trylock() always succeeds even when it is locked */ + if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) + return NULL; + if (!pcp_allowed_order(order)) return NULL; -- 2.43.0