From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 67CB642046C; Wed, 15 Jul 2026 13:00:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784120421; cv=none; b=XVfFJbozhWQb0j2kTsE0S2K0VWFsxn2I3PHHzaO5OF4XirSOXhqJx5wBiRyJ19daMYES4njsDRTNeVmWAO09N/q0W6Y2wfhJUVz5/9WQ97Jt/kZlLxo4k9xm8HQkRrgIWlGpF51zf9f0ZI5nz7VBuGUsBVOXs+OGmi+ONMPjois= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784120421; c=relaxed/simple; bh=3skrBAkbtNyg9Bumqk6FBKdNJba9ff3/9lSOe8ISDIE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CNOQVh2rkEd0ACdcVSiLR+b+KSr/gcGNJBau2nko4V9w48ds1RwRCyu6KzhfJ0M3QazSPxQldeKCCIbdFo7Zn+Bf+3HjYd3BOOoNnL0klf1JI4C/GCGxW+k2yQItf2YiYCxxdRHg8s8LEUkEjVpHyLhebJ2qJ972YqZVYKDm4ao= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ALrAJdoC; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ALrAJdoC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0C971F000E9; Wed, 15 Jul 2026 13:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784120420; bh=iawfAx9IUNsqiGi8BIPj1NgosIqnNR7z7NURj181n5E=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ALrAJdoCITv2RWPJ1pYX8IATK1b7oeIRF8Z7ES+ZMs2LU5ho4Z90RaY7B/uloe2TZ RNzHWSlRUToaosTnHHU8vdsvU1ikCVGi3uVTlWPvjzaUcCLDXI0TFwnLXOSRs/YUMf i5J3g8fP5Ph7dVazeKBaXVevZo0/GJ8fpom49TSGdgUNxK/UfAfvlaxgmVYm6yeAZE wztblW/ghKf6TSQmhlchQKCftszUm8k5yzSE7L1iw+FtDLo5CjIHI785kQHf9I8nPJ O23KxUDP7r26Dj9JqExQ+2ep2EjoLgpqHNwhC9vtLxkvElDZKPVyQjt9kVhQaehIja Dp8/8NaY/N0dA== Message-ID: <3f96edc0-229c-45c5-a9a1-852eb2de80c3@kernel.org> Date: Wed, 15 Jul 2026 15:00:14 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/page_alloc: don't spin_trylock() in NMI on UP Content-Language: en-US To: Brendan Jackman , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Zi Yan , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Alexei Starovoitov , Harry Yoo , Shakeel Butt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, sashiko-bot@kernel.org References: <20260715-alloc-nolock-fixes-v1-0-fadc49952dda@google.com> <20260715-alloc-nolock-fixes-v1-1-fadc49952dda@google.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/15/26 11:03, Brendan Jackman wrote: > As noted in can_spin_trylock(), using this is unsafe in this context. > commit 620b46ed6ae17 ("mm/page_alloc: return NULL early from > alloc_frozen_pages_nolock() in NMI on UP") fixed this on the alloc side > but missed the free side. > > Impact: If BPF programs using these features in NMI (probably tracing) > are present on non-SMP builds this might crash the kernel and is > probably exploitable by local attackers for privilege escalation. > > Reported-by: sashiko-bot@kernel.org > Link: https://sashiko.dev/#/patchset/20260703-alloc-trylock-v5-0-c87b714e19d3%40google.com?part=18 Should be "Closes:"? (Andrew can fix up locally) > Cc: stable@vger.kernel.org > Fixes: 8c57b687e8331 ("mm, bpf: Introduce free_pages_nolock()") > Signed-off-by: Brendan Jackman Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/page_alloc.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index af63558391345..5f9873dfccc5a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2979,8 +2979,7 @@ static void __free_frozen_pages(struct page *page, unsigned int order, > migratetype = MIGRATE_MOVABLE; > } > > - if (unlikely((fpi_flags & FPI_TRYLOCK) && IS_ENABLED(CONFIG_PREEMPT_RT) > - && (in_nmi() || in_hardirq()))) { > + if (unlikely((fpi_flags & FPI_TRYLOCK) && !can_spin_trylock())) { > add_page_to_zone_llist(zone, page, order); > return; > } >