From patchwork Wed Nov 24 11:58:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 12636825 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 47E5BC433F5 for ; Wed, 24 Nov 2021 13:10:55 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7DF8D6E8CD; Wed, 24 Nov 2021 13:10:54 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by gabe.freedesktop.org (Postfix) with ESMTPS id D918F6E8CD for ; Wed, 24 Nov 2021 13:10:53 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 3D6476140D; Wed, 24 Nov 2021 13:10:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1637759453; bh=quIe4/uXnU5hwY/ldEROEovl5U5E+Zhjpr5Bb6h1PF8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2JyoKDkAZCCTBuYg5Qfs0ZwJC3o164h0zXvX1Oyr87z6FQ6PqSVyqKut3tGP/9ToS FOcipPG96ktCTE3NkKac/vuQwz5QygsQyVpeZOxm8LACPWP6p7E/wpwNAbcZPFmqPk OUQr977+spQvUh3a1VZyDbG3+Cev0OzKD4S1xEFw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Subject: [PATCH 5.15 247/279] drm/prime: Fix use after free in mmap with drm_gem_ttm_mmap Date: Wed, 24 Nov 2021 12:58:54 +0100 Message-Id: <20211124115727.260910762@linuxfoundation.org> X-Mailer: git-send-email 2.34.0 In-Reply-To: <20211124115718.776172708@linuxfoundation.org> References: <20211124115718.776172708@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anand K Mistry , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, stable@vger.kernel.org, Gerd Hoffmann , Thomas Zimmermann , Greg Kroah-Hartman Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Anand K Mistry commit 8244a3bc27b3efd057da154b8d7e414670d5044f upstream. drm_gem_ttm_mmap() drops a reference to the gem object on success. If the gem object's refcount == 1 on entry to drm_gem_prime_mmap(), that drop will free the gem object, and the subsequent drm_gem_object_get() will be a UAF. Fix by grabbing a reference before calling the mmap helper. This issue was forseen when the reference dropping was adding in commit 9786b65bc61ac ("drm/ttm: fix mmap refcounting"): "For that to work properly the drm_gem_object_get() call in drm_gem_ttm_mmap() must be moved so it happens before calling obj->funcs->mmap(), otherwise the gem refcount would go down to zero." Signed-off-by: Anand K Mistry Fixes: 9786b65bc61a ("drm/ttm: fix mmap refcounting") Cc: Gerd Hoffmann Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Daniel Vetter Cc: dri-devel@lists.freedesktop.org Cc: # v5.5+ Signed-off-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/20210930085932.1.I8043d61cc238e0168e2f4ca5f4783223434aa587@changeid Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_prime.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -719,11 +719,13 @@ int drm_gem_prime_mmap(struct drm_gem_ob if (obj->funcs && obj->funcs->mmap) { vma->vm_ops = obj->funcs->vm_ops; + drm_gem_object_get(obj); ret = obj->funcs->mmap(obj, vma); - if (ret) + if (ret) { + drm_gem_object_put(obj); return ret; + } vma->vm_private_data = obj; - drm_gem_object_get(obj); return 0; }