From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96004C54EBE for ; Mon, 16 Jan 2023 15:55:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231715AbjAPPze (ORCPT ); Mon, 16 Jan 2023 10:55:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231553AbjAPPzK (ORCPT ); Mon, 16 Jan 2023 10:55:10 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ABA7822A0C for ; Mon, 16 Jan 2023 07:55:08 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 589B8B8105D for ; Mon, 16 Jan 2023 15:55:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE422C433F1; Mon, 16 Jan 2023 15:55:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673884506; bh=jaG+zHzcA6RDUPTWM3bKzkaP+3TsmEuIuLc2VeFcI8M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TJJ43Wz6mK1y4VU+Rn0Ux9d0QW0LQX7zgo+dJvBBBIGIPV/WUeWkZ6CqFNQUw4QhD hXMTrBczGWGTlgxmNP7holKwpMJGNSiGOChMMpgcGUT6CLbGNsCOlI5AYRExXmUhxH EGeX8NNX2VFe45pV4cFpLLZRI1Hmxmxy0P7wwPBs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rob Clark , Tvrtko Ursulin , Andi Shyti , Rodrigo Vivi Subject: [PATCH 6.1 031/183] drm/i915: Fix potential context UAFs Date: Mon, 16 Jan 2023 16:49:14 +0100 Message-Id: <20230116154804.670690616@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154803.321528435@linuxfoundation.org> References: <20230116154803.321528435@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Rob Clark commit afce71ff6daa9c0f852df0727fe32c6fb107f0fa upstream. gem_context_register() makes the context visible to userspace, and which point a separate thread can trigger the I915_GEM_CONTEXT_DESTROY ioctl. So we need to ensure that nothing uses the ctx ptr after this. And we need to ensure that adding the ctx to the xarray is the *last* thing that gem_context_register() does with the ctx pointer. Signed-off-by: Rob Clark Fixes: eb4dedae920a ("drm/i915/gem: Delay tracking the GEM context until it is registered") Fixes: a4c1cdd34e2c ("drm/i915/gem: Delay context creation (v3)") Fixes: 49bd54b390c2 ("drm/i915: Track all user contexts per client") Cc: # v5.10+ Reviewed-by: Tvrtko Ursulin Reviewed-by: Andi Shyti [tursulin: Stable and fixes tags add/tidy.] Signed-off-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20230103234948.1218393-1-robdclark@gmail.com (cherry picked from commit bed4b455cf5374e68879be56971c1da563bcd90c) Signed-off-by: Rodrigo Vivi Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -1688,6 +1688,10 @@ void i915_gem_init__contexts(struct drm_ init_contexts(&i915->gem.contexts); } +/* + * Note that this implicitly consumes the ctx reference, by placing + * the ctx in the context_xa. + */ static void gem_context_register(struct i915_gem_context *ctx, struct drm_i915_file_private *fpriv, u32 id) @@ -1703,10 +1707,6 @@ static void gem_context_register(struct snprintf(ctx->name, sizeof(ctx->name), "%s[%d]", current->comm, pid_nr(ctx->pid)); - /* And finally expose ourselves to userspace via the idr */ - old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL); - WARN_ON(old); - spin_lock(&ctx->client->ctx_lock); list_add_tail_rcu(&ctx->client_link, &ctx->client->ctx_list); spin_unlock(&ctx->client->ctx_lock); @@ -1714,6 +1714,10 @@ static void gem_context_register(struct spin_lock(&i915->gem.contexts.lock); list_add_tail(&ctx->link, &i915->gem.contexts.list); spin_unlock(&i915->gem.contexts.lock); + + /* And finally expose ourselves to userspace via the idr */ + old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL); + WARN_ON(old); } int i915_gem_context_open(struct drm_i915_private *i915, @@ -2199,14 +2203,22 @@ finalize_create_context_locked(struct dr if (IS_ERR(ctx)) return ctx; + /* + * One for the xarray and one for the caller. We need to grab + * the reference *prior* to making the ctx visble to userspace + * in gem_context_register(), as at any point after that + * userspace can try to race us with another thread destroying + * the context under our feet. + */ + i915_gem_context_get(ctx); + gem_context_register(ctx, file_priv, id); old = xa_erase(&file_priv->proto_context_xa, id); GEM_BUG_ON(old != pc); proto_context_close(file_priv->dev_priv, pc); - /* One for the xarray and one for the caller */ - return i915_gem_context_get(ctx); + return ctx; } struct i915_gem_context *