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 X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2BA5C43381 for ; Fri, 1 Mar 2019 23:06:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 751552083D for ; Fri, 1 Mar 2019 23:06:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="JQssBqN1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726337AbfCAXGT (ORCPT ); Fri, 1 Mar 2019 18:06:19 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:38908 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725934AbfCAXGS (ORCPT ); Fri, 1 Mar 2019 18:06:18 -0500 Received: by mail-pg1-f196.google.com with SMTP id m2so12125853pgl.5 for ; Fri, 01 Mar 2019 15:06:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=WwRwUOwBbuqqde4cgzaMzPICNmEeL7GCcGUf5rgy3ZA=; b=JQssBqN1rIGozFmTM+mNcJLXnphppLxnyckzsC9gT3n8Mvm/OR7+YEXl5ZZOGpJ2ri +y8kHEKbKGIV7uiNnL5hE+qlsorZn9r4fXnnmRBm0+1vJMR5jhDr7C+kvFu1D0Juzr0c EngPIoq8ey/335MtPofwRRPsW1WRabB5nLsT8pEJ+f6gMsUxtZ+da14Tmat7YDiFslbf EZrDEkoelt3FOr5tpDt+REEsB10e7ApJ7QcVC7R8FtbuLGSXUE3cwvz+iXygSfa6EmK+ tw84yTt0EvwfUrbOfR94m7oH7ZERcrLflkkFrJxUOhEbRBWAd7ZZOUtZR9zXQCHagkyB oEqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=WwRwUOwBbuqqde4cgzaMzPICNmEeL7GCcGUf5rgy3ZA=; b=oP6WwF5N3G8QGt++tui7nc5cSfjIi2pm22RfRnW3BVoJ/h8a5a1B5+rbhNDkKTj5pf BU1n+v3HCrcU/hJUvapO0PjKEGqOPBaCbcaEr5qA2Na0NG6SdmSyq6ebQXOCUNyPmjpn k4CdWmcBCsGVLchQr0clp8wLZbqELIqH2JnBVw+taDSL9WrV4qKtyBGHjrRo/BT+H8HU omUkGyX6irDGjG793TOx2sQV/lpp2ErJGOTdHbp9rHU+vuu5DGC8io5+M+Cqk7V93WlT bTReGirwTkTk5CKhxF+zBgDmd153SYAaXr/Zi+MmtCmMtrVX+KcLbr1263aliL7z32Ar kSNg== X-Gm-Message-State: APjAAAWkBTyTrtAAyb3HAXdq6EstH8za1nd8Iwvwr1Cp4C0vFfOJsL3n gos3EMidwJDRgMwozQPEUh0J9A== X-Google-Smtp-Source: APXvYqyjoyHI3j6XtKcXk0PR+CvaiwLZvBVP5Jmr8U3qpm67Dt/GHPDniOkH6++1SG7Den2vio3O5w== X-Received: by 2002:a63:1723:: with SMTP id x35mr7120923pgl.364.1551481577713; Fri, 01 Mar 2019 15:06:17 -0800 (PST) Received: from ava-linux2.mtv.corp.google.com ([2620:0:1000:1601:6cc0:d41d:b970:fd7]) by smtp.googlemail.com with ESMTPSA id e22sm13252259pfi.126.2019.03.01.15.06.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 01 Mar 2019 15:06:17 -0800 (PST) From: Todd Kjos X-Google-Original-From: Todd Kjos To: tkjos@google.com, gregkh@linuxfoundation.org, arve@android.com, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, maco@google.com Cc: joel@joelfernandes.org, kernel-team@android.com Subject: [PATCH] binder: fix race between munmap() and direct reclaim Date: Fri, 1 Mar 2019 15:06:06 -0800 Message-Id: <20190301230606.8302-1-tkjos@google.com> X-Mailer: git-send-email 2.21.0.352.gf09ad66450-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org An munmap() on a binder device causes binder_vma_close() to be called which clears the alloc->vma pointer. If direct reclaim causes binder_alloc_free_page() to be called, there is a race where alloc->vma is read into a local vma pointer and then used later after the mm->mmap_sem is acquired. This can result in calling zap_page_range() with an invalid vma which manifests as a use-after-free in zap_page_range(). The fix is to check alloc->vma after acquiring the mmap_sem (which we were acquiring anyway) and skip zap_page_range() if it has changed to NULL. Signed-off-by: Todd Kjos --- drivers/android/binder_alloc.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 6389467670a0b..195f120c4e8c9 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -927,14 +927,13 @@ enum lru_status binder_alloc_free_page(struct list_head *item, index = page - alloc->pages; page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE; + + mm = alloc->vma_vm_mm; + if (!mmget_not_zero(mm)) + goto err_mmget; + if (!down_write_trylock(&mm->mmap_sem)) + goto err_down_write_mmap_sem_failed; vma = binder_alloc_get_vma(alloc); - if (vma) { - if (!mmget_not_zero(alloc->vma_vm_mm)) - goto err_mmget; - mm = alloc->vma_vm_mm; - if (!down_read_trylock(&mm->mmap_sem)) - goto err_down_write_mmap_sem_failed; - } list_lru_isolate(lru, item); spin_unlock(lock); @@ -945,10 +944,9 @@ enum lru_status binder_alloc_free_page(struct list_head *item, zap_page_range(vma, page_addr, PAGE_SIZE); trace_binder_unmap_user_end(alloc, index); - - up_read(&mm->mmap_sem); - mmput(mm); } + up_write(&mm->mmap_sem); + mmput(mm); trace_binder_unmap_kernel_start(alloc, index); -- 2.21.0.352.gf09ad66450-goog