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 CEF6037C901 for ; Thu, 9 Apr 2026 12:36:33 +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=1775738193; cv=none; b=qUsGUTwox+CwHSsMrTn4Sn8WjyXctWDOsXY5Hyp017ufgXPnR076JHpbmXBQMmbKD4ezpfJ9JLjztuyjppLzo+8SZVmESgNZEDzNRI52Xt+FuooNwxDG66t8tdWgqtNAElwTGlifIkIpUeKh3yF2+irNaZbOUKKhIvFOIf+z5sU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775738193; c=relaxed/simple; bh=kM9h+y0BF4ZFQcAKpgEEGNTYcYx79nYyDjyV7OihopE=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=t0ZIrBAuT5y7VJuCefhCMu55VmnXHE5aX/j4IPSudiyGFPgEL2iWpi0OEdFGgEHeKQTtqXB8zkwNgGZqw6bP99iv3qzF5WxY8F2fGQS65ed+0KYaJvlvZWH/tgozILyaiJAE8Lzfqun8+sQG1K5IYZBZTav4ycbmaZNB8j08rM8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JljPoIvC; 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="JljPoIvC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 707D4C19424; Thu, 9 Apr 2026 12:36:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775738193; bh=kM9h+y0BF4ZFQcAKpgEEGNTYcYx79nYyDjyV7OihopE=; h=Date:Subject:To:References:From:In-Reply-To:From; b=JljPoIvCiph2RcjwcnpjoOccsbVu7nZdIl1DZADymDX8dosQ8++Iux80DZMoztID7 nQxXg887ByeclE9szJzYeKOGbLCmIGZ6kSiVvL28/UzshUjmxEzSrZxekVE7scs54C 56fw3CWwDn6uNLAfEphEykQuxW95QpfLLT26bWK3U1lA17thvSRmlh1W0hjVKIDW4l 1Am4g+YymGPFyy0NDkxsHsZd1ys40FxpJE2dXOBVzZ8dzrpHezlJhl/Wza4pAnPf36 SxNLWTE5db2o9d0NOqI5OWZtWJkNNWVuv9N6y+4jpRCqQBkvDi2RfWYu21f44Qt2j4 uTSBBOakJ/vlA== Message-ID: <3bcd073e-f142-4e7c-8d5e-b0d1239ca9b9@kernel.org> Date: Thu, 9 Apr 2026 14:36:25 +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 4/5] riscv: mm: Fix NULL dereferences in napot hugetlb functions To: Michael Neuling , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , "Mike Rapoport (Microsoft)" , "Vishal Moola (Oracle)" , Albert Ou , Aleksa Paunovic , Aleksandar Rikalo , Alexandre Ghiti , Andrew Jones , Andrew Morton , Arnd Bergmann , Djordje Todorovic , Guo Ren , Junhui Liu , Kevin Brodsky , Lorenzo Stoakes , Nam Cao , Oleg Nesterov , Oscar Salvador , Palmer Dabbelt , Paul Walmsley , Qinglin Pan , Raj Vishwanathan4 , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org References: <20260409091143.1348853-1-mikey@neuling.org> <20260409091143.1348853-5-mikey@neuling.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/9/26 11:11, Michael Neuling wrote: > huge_pte_offset() can return NULL when any level of the page table walk > encounters a non-present entry. Both huge_ptep_set_access_flags() and > huge_ptep_set_wrprotect() re-derive ptep via huge_pte_offset() in the > napot path but use the result without a NULL check, leading to NULL > pointer dereferences in get_clear_contig_flush() and set_pte_at(). > > Add NULL checks after huge_pte_offset() in both functions. > > Fixes: 82a1a1f3bf ("riscv: mm: support Svnapot in hugetlb page") > Signed-off-by: Michael Neuling > Assisted-by: Cursor:claude-4.6-opus-high-thinking > --- > arch/riscv/mm/hugetlbpage.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c > index a6d217112c..7d155341cf 100644 > --- a/arch/riscv/mm/hugetlbpage.c > +++ b/arch/riscv/mm/hugetlbpage.c > @@ -288,6 +288,8 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma, > order = napot_cont_order(pte); > pte_num = napot_pte_num(order); > ptep = huge_pte_offset(mm, addr, napot_cont_size(order)); > + if (!ptep) > + return 0; > orig_pte = get_clear_contig_flush(mm, addr, ptep, pte_num); > > if (pte_dirty(orig_pte)) > @@ -335,6 +337,8 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm, > order = napot_cont_order(pte); > pte_num = napot_pte_num(order); > ptep = huge_pte_offset(mm, addr, napot_cont_size(order)); > + if (!ptep) > + return; > orig_pte = get_clear_contig_flush(mm, addr, ptep, pte_num); > > orig_pte = pte_wrprotect(orig_pte); These functions are called when we previously verified that there is indeed a pte mapped. And while holding the PTL to protect concurrent unmapping. So how should this possibly trigger? -- Cheers, David