From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B827A3C09E1; Tue, 16 Jun 2026 18:03:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781633014; cv=none; b=fTNsG0lLBy8SoK5p3XWwUGfGMYNol1HvAtZCPLnt1nd4oRGyYadOCWCWM7l9BethQb/T/mx8Eg0wgQsJpPNLQ9li6K2PyiED/AUi98C8GglqBGOyXr+Gfs35obg3Gj/cKVhMyJnyezg49a/AOduBWgfjxgUcSP+EvJ9M2ZWU1H8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781633014; c=relaxed/simple; bh=LT7cBtNoCJTHsZ5AjA3AKuHy5uCufNXl/biROmaDnhs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=oSqAT81JvMlsdZSYQtiNy0/z4vVRgdrgPuuy9dccp0WOhHTA/A7FXkquEtLaJS8Z4caD6RPYo19/0NVFK87hGxdbvmQufyBGnM5rWdnbXTGrHNc38Wp9fveF7Q0naS8/VEW8+3NnmK0jdDRVDqR21Dp277Z8X2byT4SPxgjKTZc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gGdPRqK2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gGdPRqK2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C066E1F000E9; Tue, 16 Jun 2026 18:03:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781633013; bh=UEeopNKKF4RX2tLGKDtBQeODKbeyeQoVx+aWH94qGUc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gGdPRqK2Om1YPVwYiaI2mw25NEuAk1Glv/cmezhH0YgqOiak3Nw12rqRlKW26equt fvRDwUptS+y1O8nnFmcWe5y+TobH8amYrE+R3YplRdRkvdzysDATM3416xXA3EqTm4 yPwwqpXt8Kc5dbPlJoRr68TJaXy2e9kxiwjsqORE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ashutosh Desai , =?UTF-8?q?Ma=C3=ADra=20Canal?= Subject: [PATCH 6.1 512/522] drm/v3d: Reject empty multisync extension to prevent infinite loop Date: Tue, 16 Jun 2026 20:30:59 +0530 Message-ID: <20260616145149.691657860@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145125.307082728@linuxfoundation.org> References: <20260616145125.307082728@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ashutosh Desai commit fb44d589bf3148e13452185a6e772a7efbf2d684 upstream. v3d_get_extensions() walks a userspace-provided singly-linked list of ioctl extensions without any bound on the chain length. A local user can craft a self-referential extension (ext->next == &ext) with zero in_sync_count and out_sync_count, which bypasses the existing duplicate- extension guard: if (se->in_sync_count || se->out_sync_count) return -EINVAL; The guard never fires because v3d_get_multisync_post_deps() returns immediately when count is zero, leaving both fields at zero on every iteration. The result is an infinite loop in kernel context, blocking the calling thread and pegging a CPU core indefinitely. Fix this by rejecting a multisync extension where both in_sync_count and out_sync_count are zero in v3d_get_multisync_submit_deps(). An empty multisync carries no synchronization information and serves no useful purpose, so returning -EINVAL for such an extension is the correct defense against this attack vector. Fixes: e4165ae8304e ("drm/v3d: add multiple syncobjs support") Cc: stable@vger.kernel.org Signed-off-by: Ashutosh Desai Link: https://patch.msgid.link/20260415050000.3816128-1-ashutoshdesai993@gmail.com Signed-off-by: Maíra Canal Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/v3d/v3d_gem.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/gpu/drm/v3d/v3d_gem.c +++ b/drivers/gpu/drm/v3d/v3d_gem.c @@ -649,6 +649,11 @@ v3d_get_multisync_submit_deps(struct drm if (multisync.pad) return -EINVAL; + if (!multisync.in_sync_count && !multisync.out_sync_count) { + DRM_DEBUG("Empty multisync extension\n"); + return -EINVAL; + } + ret = v3d_get_multisync_post_deps(file_priv, data, multisync.out_sync_count, multisync.out_syncs); if (ret)