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=1794047581; b=H9cbPkTCoWMkhz71AAuCWFHNu+PFAsZ3ngnHMftrYnlMV4poDiHueOZr5rWBII5DgKb4 lqFYIWBLR6+CYadgiJl6A4BMEn7Shbm5G/EGj3zUGV83Iibna6xF0HMnnqgkepFtk2NpK Hld59RCpqhfI0X+28wjTmuGrTh1EdAxE5gBGYcbNpzWqfMQWHh84gJEUztjOAknZu272s Ldqbz/kSe+C1U7ABnHWsNSk+/xu0ai+//ZiIgVt5OSSzYeT+EOohPNli5MqwPI2clTlr8 8mahmjzVpr2BwvknApoihPrrm3j73BmLJuLVR8bDaw6BEWPiHW4ZCKpiWS6cTuEi4Dg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047581; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=XY4d4WXzs8UuiFBvvYVoFw6EKYdQPjvaVN34IOWgkQU=; b=ka2OOy2Lyorf0Ccer6JRMSlXo1H7idjW/vLcC3S07P7Dc9gQwULe4hgIuqYqGb15PvUm unnyikKd0j8a51CqeYkMmz4c8GzRVlt1U2f2cdUEa6kxAOv0W7DSK2EmVFsRmWF/QQTST JkTdiOaL6rH5rKsZQsqKsj2vhQfovSLZiz81jxTptixU4H/TuvptermLrOUnG/YcG61dx VJ+1tWAmb2WqzWSwA2hb/aCIo7iZC6ejJarvH4m2PsaNdLj0FCZVN6r+sz68fmzLYyfI6 VWufq+wlalS7khMCacIkucaHuMzshr9JIFqyPVQGvmX+ilQv+Y0q68tQI4EO1QtOSPw== 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=f3fF1AJb; 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 098B1606A32C for ; Sat, 7 Nov 2026 10:33:01 +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=f3fF1AJb Received: by smtp.kernel.org (Postfix) with ESMTPSA id 640381F0089F; Sat, 7 Nov 2026 10:32:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047580; bh=XY4d4WXzs8UuiFBvvYVoFw6EKYdQPjvaVN34IOWgkQU=; h=From:To:Cc:Subject:Date; b=f3fF1AJbY9xwO10Mxhs5S3Irp8W7PkYBaNNtwdgKQ34ZskLSTaXPUqI+7NNG6mtro 5MZgwnmWD7z/Ps74JBpIygHne0hoprOLAda++IcpFQRLYRjBvF5bJtzrPaykq5sTKB VRjfAcOlE8HZtbXAb/jMv5PuEShnl5jCY87vfOdWvyZDGYsCO9JS07Sw6g3wdNJjA4 XJvnzUrIg3ProE6Kz0ThJxdQuB3uCgXAfTenZNe56O+4bqelPddVs4FPXrSUhUk2TT p7+cfDxvE5E3S+Kh0dQKjaRwZDMUsZBgGxWeJI0ELbUf0HEbtTuyoHXBKHfIklZWK1 umKkEFpA1ruRA== 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 6.6-stable tree Date: Sat, 7 Nov 2026 05:32:58 -0500 Message-ID: <20261107053258-failed-6.6-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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x ae0298a5fbeff32951c0d31398ccec97ec6aa0ea # git commit -s git send-email --to '' --in-reply-to '20261107053258-failed-6.6-ae0298a5fbef@kernel.org' --subject-prefix 'PATCH 6.6.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