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=1794318175; b=5mN2IkzjWGInwnuEbtYQf86OM6VqPC91YkzeDlrFTZE81ZqZVr1cAhL0HSIUM4hsZDhu Z5S4BjTtwhEsmGOvtUjr0MOBhTIRJZf6atPT0crG8MtJvKjfHP8rWj8vfDUtaZHacU6mw ETMwcnXlV1wsUK7UAfPHsp7Pr5GeaL+QHzEteGBjDCoXMRWYFJ4oSXzktn35boX18Jti6 nxXv6Uh2tGrnkuy3+amoSTkFJzHOIXiF8assT3eb8txFFh0Cdjex7MG+YxdNWPxCM6m4I sUmjYDSXmIQkMGpHPPx68OvXDmw0EIJVlpw7d2cZHef/c90YzCFT99G9bLI4i2V+IlA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794318175; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=cegQ1B36SRGNswGq2aaJJvWVsTsz+N1PSENk04DxN7I=; b=pefQNnygENVyg++JdMYXAYcjEpTeo81eQlvsXS4/HIXLDMA//UiMm4TL+aEzdg24Di+I XhRNNGFdIR0Aw84TkNyLQ5OX1GBJVpCIRTFq3IYsD94tsDydgy3OuD9UmUCNH+AOyIXel h1yy+pm0p3VesxPcq1qcb1Cpt0jw+gYqDmsizlgaXs0HyWWG6mlMmHBz3EEAwjaeFK8ts ig/V33YkkUYOUYo1Tm9hof8RW2Cqvc+CeAJIOBsfcLN2tIxqo2zW7dtnDM8LGqzW9PINx 3zdp+livB0reMTL5xKq4460usGcAKpw3/zVFvnzIXeln4Kn4vFiVgBydVAFV6eYvXOA== 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=gehbi1U7; 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) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93CBE606A321 for ; Tue, 10 Nov 2026 13:42:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=gehbi1U7 Received: by smtp.kernel.org (Postfix) with ESMTPSA id C62D51F0089F; Tue, 10 Nov 2026 13:42:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794318175; bh=cegQ1B36SRGNswGq2aaJJvWVsTsz+N1PSENk04DxN7I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gehbi1U7+ZjAJoVwnNikm/yVOsvpTwc0kKJ3SoWmnPQ7HN7MRzhadbWEj1HOhonTy k7K6vjvpEWJH2KCOSwv8XEl8dVbmn5A4cVX0t1t5MllAzp6EwUITvLqisEgpa1dxnp 7b4cBx/g/CvJFM6/Vwe3AevJ34d7rc2faBIyZLehFExyU0hoUVdQ7/Un/28pWTx5zZ sIy5ygaQDpnwzT/wZ+DGikjXI/5D0ih77WiwbEUIULgw6BkutJipEREJP15KS94GES KAP9DoV75yR42F+46JbkM8ikSocjXFXpn49ArQ9Vp4+sAZHGGvy4104lDxD2vXpptq cy8fSv/4Cyr7Q== From: Sasha Levin To: stable@vger.kernel.org Cc: Abdifatah Suruur , Juergen Gross , Sasha Levin Subject: [PATCH 5.10.y] xen/gntdev: prevent private mappings from becoming writable Date: Tue, 10 Nov 2026 08:42:53 -0500 Message-ID: <20261110134238.1758836-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107062010-failed-5.10-2176dea8d8c1@kernel.org> References: <20261107062010-failed-5.10-2176dea8d8c1@kernel.org> 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 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> [ sashal: Replaced unavailable vm_flags_clear(vma, VM_MAYWRITE) with vma->vm_flags &= ~VM_MAYWRITE. ] 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 06511e67fa520..8af9c86e0fd99 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -1064,6 +1064,13 @@ 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)) + vma->vm_flags &= ~VM_MAYWRITE; + pr_debug("map %d+%d at %lx (pgoff %lx)\n", index, count, vma->vm_start, vma->vm_pgoff); -- 2.53.0