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 72C0D2590 for ; Sun, 22 Jan 2023 15:23:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5A8BC433D2; Sun, 22 Jan 2023 15:23:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1674401015; bh=/q6rBZOT3WgoBAtjuHryok5+JLfH9kF2NqsGIKwugmM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2I+E7+VMwI9t3yVVdpwAcvJ+zG0Gwk3dbT9eGFTRFp5ezca9EyT5FeJVd8M43pSwi s2YVzl4y2rhUjEFF1XiNXUrGZVrfO3QmMx88V8i5SzXoh3/r8AQfAXQ60f8/gBQuBG QbacgAgrqf/wjgnGyaiwththiVBuonsOXyg+mAt0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Peter Xu , James Houghton , Mike Kravetz , David Hildenbrand , Andrea Arcangeli , Axel Rasmussen , Muchun Song , Nadav Amit , Andrew Morton Subject: [PATCH 6.1 078/193] mm/hugetlb: pre-allocate pgtable pages for uffd wr-protects Date: Sun, 22 Jan 2023 16:03:27 +0100 Message-Id: <20230122150249.919860960@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230122150246.321043584@linuxfoundation.org> References: <20230122150246.321043584@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Peter Xu commit fed15f1345dc8a7fc8baa81e8b55c3ba010d7f4b upstream. Userfaultfd-wp uses pte markers to mark wr-protected pages for both shmem and hugetlb. Shmem has pre-allocation ready for markers, but hugetlb path was overlooked. Doing so by calling huge_pte_alloc() if the initial pgtable walk fails to find the huge ptep. It's possible that huge_pte_alloc() can fail with high memory pressure, in that case stop the loop immediately and fail silently. This is not the most ideal solution but it matches with what we do with shmem meanwhile it avoids the splat in dmesg. Link: https://lkml.kernel.org/r/20230104225207.1066932-2-peterx@redhat.com Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes") Signed-off-by: Peter Xu Reported-by: James Houghton Reviewed-by: Mike Kravetz Acked-by: David Hildenbrand Acked-by: James Houghton Cc: Andrea Arcangeli Cc: Axel Rasmussen Cc: Muchun Song Cc: Nadav Amit Cc: [5.19+] Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6604,8 +6604,17 @@ unsigned long hugetlb_change_protection( spinlock_t *ptl; ptep = huge_pte_offset(mm, address, psize); if (!ptep) { - address |= last_addr_mask; - continue; + if (!uffd_wp) { + address |= last_addr_mask; + continue; + } + /* + * Userfaultfd wr-protect requires pgtable + * pre-allocations to install pte markers. + */ + ptep = huge_pte_alloc(mm, vma, address, psize); + if (!ptep) + break; } ptl = huge_pte_lock(h, mm, ptep); if (huge_pmd_unshare(mm, vma, address, ptep)) {