From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794046823; b=dfANwk/LL8KMMwVO5wnujEeHFtUF9T9OGimWLcdUeT3dOBs8F2XXLOwXgrtRxxaw4X72 k7zticeNd9pR/KDxF4yssrqCD5Wit9trV477jJXziBnYxgPrubwqEzfOcAaunKQGL8jdK XGvCKGarzpqBmoD1EeqS102fvRnaof4QOLZJXFu3RlfXasR3NiOVuAy3ytTS1LQhdEgK4 aRcJ5wtU/ix9koCDxOOj1Kbv7XQriwazLIOn6Pw9upjojnuiZWSJ2VkAxWDeK3jY7qyHC cX8NExVOKOafZo0I2nykJxKU+FERemSfXg4TM/xw8deYHWiNQaV3BKVkhH38/GFD0uw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794046823; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=Kjb73h3nFQR3LGOivYkEGD4pODkGUwk15gOTAGDttOo=; b=ICA1bf2XFqYrSziqzaYN/QJiOTd47Y4I5YCrC6E4WN6pPG9WRvS8Tm5NR1mtTE7BqsWQ MKL8fZ9LLfG3wFazIQsJ/3N/YOWGgb05/pq0K4BZamOZv1AmAJgzsqFjgz9uPr07cf9jz ylvKGGZGtKntwS2RCfihgfWb/jw6wJHuxClbvQErgLa44FBDyuK7rG+kbkpT8qUGW4r9q HEVzFafp0NLMkEu4j2gc9jGxd/yJh026egs4OGzgEN6QMDkZo/fNMEDaIT2n+dOZMRNEz P8YMyuXmAxhxzY53yVWIX5/749BepRMx4iMMYWnKidbBrjAYtNJS2OX9xAPzZQlcF2Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=HLKuBYjV; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 11020606A33E for ; Sat, 7 Nov 2026 10:20:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=HLKuBYjV Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9139B1F0089F; Sat, 7 Nov 2026 10:20:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794046822; bh=Kjb73h3nFQR3LGOivYkEGD4pODkGUwk15gOTAGDttOo=; h=From:To:Cc:Subject:Date; b=HLKuBYjVySyFp+BCcJ7MQFslHEsn7QYxBV8fr+aZySXeM/5umEoRpg8/wvHzVLfdc Nvz4og2oPpfk9xdef/KFAI1h2eARM3vshsss7SopohLKtjjpQY7k9WY7SOAhjj6IJ3 MtBqH5Oy+rUz5k7hqUrliJeFX1xdnG4/2FC1PXhVaPFwEISzVCiVQei7soy/CTGmfx z3dCPQlCCAue07J2FmTGvm26CW9hJtZ4aW7CtvkBhbgY0dfzgy2UL5BmGegJt+c3pk Sc3yqBceF88sJQkuKXY/2bYSdOJeYEnsyArcZClMFRycYl6oujxZ8ds4Frf+4V14xf dq6LaYYBLd4rw== From: Sasha Levin To: rakukuip@gmail.com, weir@nebusec.ai, akpm@linux-foundation.org, vega@nebusec.ai, david@kernel.org, notasas@gmail.com, liam@infradead.org, ljs@kernel.org, mhocko@suse.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/memory: constrain generic_access_phys() to page boundary" failed to apply to 6.12-stable tree Date: Sat, 7 Nov 2026 05:20:20 -0500 Message-ID: <20261107052020-failed-6.12-ae0298a5fbef@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x ae0298a5fbeff32951c0d31398ccec97ec6aa0ea # git commit -s git send-email --to '' --in-reply-to '20261107052020-failed-6.12-ae0298a5fbef@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From ae0298a5fbeff32951c0d31398ccec97ec6aa0ea Mon Sep 17 00:00:00 2001 From: Luxiao Xu Date: Thu, 10 Sep 2026 11:42:50 +0800 Subject: [PATCH] mm/memory: constrain generic_access_phys() to page boundary This patch addresses an issue in generic_access_phys() where accessing memory across page boundaries in PFNMAP VMAs assumes physical pages are contiguous, which can lead to accessing unintended physical memory or exceeding VMA boundaries. generic_access_phys() improperly validates the memory access range: it only validates the start address using follow_pfnmap_start() and passes PAGE_ALIGN(len + offset) to ioremap_prot(). This poses two problems: 1. In PFNMAP VMAs, consecutive virtual pages are not guaranteed to be physically contiguous, and individual PTEs may have different access permissions or writability. 2. The mapping may cross VMA boundaries if len extends beyond vma->vm_end. Constrain the access in generic_access_phys() to at most the current page boundary (PAGE_SIZE - offset) and map only a single PAGE_SIZE via ioremap_prot(). Since the caller __access_remote_vm() already loops over the requested length and handles partial transfers, it will naturally iterate over the remaining pages. Also add a missing (resource_size_t) cast during PFN re-validation to avoid truncation on 32-bit PAE systems. Link: https://lore.kernel.org/e06e28a46c2a176238f03b5740df0913e57c2861.1788842306.git.rakukuip@gmail.com Fixes: 9cb12d7b4cca ("mm/memory.c: actually remap enough memory") Signed-off-by: Luxiao Xu Signed-off-by: Ren Wei Signed-off-by: Andrew Morton Reported-by: Vega Suggested-by: David Hildenbrand Acked-by: David Hildenbrand (Arm) Assisted-by: LLM Cc: Grazvydas Ignotas Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: --- mm/memory.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index ec63dd6212ac5..926276d419202 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -7131,6 +7131,12 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, bool writable; struct follow_pfnmap_args args = { .vma = vma, .address = addr }; + /* + * Limit access to one page at a time, as that's what follow_pfnmap_start() + * guarantees; expect the caller to retry to read larger ranges. + */ + len = min_t(int, len, PAGE_SIZE - offset); + retry: if (follow_pfnmap_start(&args)) return -EINVAL; @@ -7142,7 +7148,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, if ((write & FOLL_WRITE) && !writable) return -EINVAL; - maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot); + maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot); if (!maddr) return -ENOMEM; @@ -7150,7 +7156,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr, goto out_unmap; if ((pgprot_val(prot) != pgprot_val(args.pgprot)) || - (phys_addr != (args.pfn << PAGE_SHIFT)) || + (phys_addr != ((resource_size_t)args.pfn << PAGE_SHIFT)) || (writable != args.writable)) { follow_pfnmap_end(&args); iounmap(maddr); -- 2.53.0