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=1794064617; b=wNi4dmHcVWxaHC/xMgIh+Gb7WqCm4K7bGTnrGUEtD8OTFBdCI2maxoTxIgsvpmZTlI+4 WyVbhnZy39kVEuXUzD8W38/KolPMWuASlAabehQcSMn45MG00O/lga1hHrXiJpHjwWOMZ bFe3KbeBlfHu+bsce7/5IvCndjbLAq5G+6uevNdXO13vzJ34UczGoACgoHnrp0WpO1Ic6 Z6/m0s8j/O5eU6UpgerYAwjnGp/nV1eQRBCRgEaJSEo0cqCQTjiYt4hjWoyOl19Bl/PVH ROGX0lZZs4e8b3CI+xUXQnDRG2frnWlDn8R0Yj0pk6MPZxkKZ8Tj6ubwbNq9ZgAoc4g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794064617; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=Nw8763Ueenrb+3yn6P62mrlipIJKVtZmA12fmE9MIWM=; b=udW+RbP5iyDj10u6Rn38rVcIa8G061Nbagmo8GoaPIiJ9rLIoP1PXaV33q7JfBnc7Fav ehBiUFUMcHxYA5r29mpjyC0FNE7NxsNkmaI/HycBi+IjdWNvP2yBqG1qkAC7Y9tvrV5x6 fpJ5KiY4kVqljATUHDmNiyQf8i4l0EvtUPGzvXF5gyDZlNp77Raq3k6ZqSPUaMQkHHkWB OqUJwtdACN0CA1Zm9PhXxR3Iugs+dDhscUAij9jdWOD05FQSlvM6TjZM0/YSzrlZj2ydS JIprRsAOzYlNLJ17mhcF1jl8wfgjpaj84YGLDTmypnN865YQW9Gzv7tOr+Aaxu28hGw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=XzLnZz8x; 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 7294C606C006; Sat, 7 Nov 2026 15:16:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=XzLnZz8x Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FAED1F0089F; Sat, 7 Nov 2026 15:16:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794064617; bh=Nw8763Ueenrb+3yn6P62mrlipIJKVtZmA12fmE9MIWM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XzLnZz8xM3VKwf66sXwL6VrF0TA+u3FGpkDFVtScwIaLGX5VGNCqv9DnAwy0xIjPJ IEOtdeRHbKG9LmvtA9fP31yYy0ZEGDKHRoq8mkjUc4b3vnavtOAM/VHKPQsQoyOo1w TNk0VCOqbvegSm5gqoqHC3MUW3CCSM5qlJESbCKc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Abdifatah Suruur , Juergen Gross , Sasha Levin Subject: [PATCH 7.3 0589/1257] xen/gntdev: prevent private mappings from becoming writable Date: Sat, 7 Nov 2026 08:48:05 -0500 Message-ID: <20261107134955.608609438@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134939.434104957@linuxfoundation.org> References: <20261107134939.434104957@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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-Transfer-Encoding: 8bit 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Abdifatah Suruur [ Upstream commit 2176dea8d8c19cb43a9b3651bfa1cb21eab1b31a ] gntdev_mmap() rejects writable private (non-shared) mappings of foreign grant pages, because a private writable mapping takes the COW path on pages that have no proper struct-page backing. However, VM_MAYWRITE is left set, so userspace can map the grant read-only and then upgrade the mapping to writable with mprotect(), hitting the same COW path the check was written to prevent. Clear VM_MAYWRITE for private mappings, as i915 does for its read-only objects and as fixed in drm/vc4 (CVE-2026-68445) and drm/panthor (CVE-2024-53071) and ptp: vmclock (commit a5edadbae57e2298a56cf7a4e774a027905a331f). Fixes: ab31523c2fcac ("xen/gntdev: allow usermode to map granted pages") Cc: stable@vger.kernel.org Signed-off-by: Abdifatah Suruur Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Message-ID: <20260819084217.1577-1-suruurism@gmail.com> Signed-off-by: Sasha Levin --- drivers/xen/gntdev.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 1dcc4675580ed..b71f5bae25b63 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -1066,6 +1066,13 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED)) return -EINVAL; + /* + * Private mappings of foreign grant pages must never become + * writable: they would take the COW path on granted pages. + */ + if (!(vma->vm_flags & VM_SHARED)) + vm_flags_clear(vma, VM_MAYWRITE); + pr_debug("map %d+%d at %lx (pgoff %lx)\n", index, count, vma->vm_start, vma->vm_pgoff); -- 2.53.0