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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 84867C433E1 for ; Thu, 11 Jun 2020 11:44:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E4B42072F for ; Thu, 11 Jun 2020 11:44:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="AzLoTv6l" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727780AbgFKLoc (ORCPT ); Thu, 11 Jun 2020 07:44:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726697AbgFKLob (ORCPT ); Thu, 11 Jun 2020 07:44:31 -0400 Received: from mail-pf1-x442.google.com (mail-pf1-x442.google.com [IPv6:2607:f8b0:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7FEF5C08C5C2 for ; Thu, 11 Jun 2020 04:44:31 -0700 (PDT) Received: by mail-pf1-x442.google.com with SMTP id b201so2584339pfb.0 for ; Thu, 11 Jun 2020 04:44:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=NeR4sKutcrUPwtCckv6Tmqw2IkRMLX24dUiE+CNNtLg=; b=AzLoTv6lnntU3TjLLEgR6fmbijpMmaW1TiVxBsvjGtDygCtFgSsOhUr/x580awC9CJ OWtjuYN91NakIQ0xzJBT44oS7XlppiYpQRPzAIXpeYUcqXzSpm9t2pxKcFM8ltkRm4Qy TviFdnkCDQhhB6Ksg6B+/zb6ZBTNWHgNi1TUJ7AYJQgRbi7MVRHjTB1c0e53WO2aIhus E28nJ9MuYhrO7fmnxZzxlp4KUMsOHAZ7mv4R33BjeWS8OFVUVsDdgxd+0QROsIrmHkxg 8lSPIeygynVgxIQizbR19HoEhoM9eN3KtFFM1P8Din25DLW9W/lBzQHWmvhhVFPkIyX6 7qjQ== 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=NeR4sKutcrUPwtCckv6Tmqw2IkRMLX24dUiE+CNNtLg=; b=aMgaPbbOjUO890Vs9gFrWexywTSo+Q0kTSvXl1S9ijpXulu1akSyhiFfaNHW8ZfgG2 lLeET24eCHsVPpScUUKSufysW3cY1vYij9+jTXA8kfM7k9I1zSRz7IUWefyDTIdZ+UZ4 duoBGPL/jmIZP6Zm5pYAkbnUr7DfX4rsaZeGsErzbySSavY2dCqSJsuskhzOKN/FOag6 s3jIDw4fJfqhG8axDFbII3287ox+FcfxXJb1x/4JqNQiC9KPDaWWFvp/z58/D91KuZq4 vOXjjsMk95nRhGGR23OscYfnYv6fNxDN+GZxjotshrwO6AzV/I79JS5idJWZgMUdjgpO zqxg== X-Gm-Message-State: AOAM531UiAWqPI9PRESXFeScAHebxSxrQ/FBph9erFJ6r+u7VJ3WhvBo lplveb99GTZ5vK0N5caaXg71bg== X-Google-Smtp-Source: ABdhPJxIOHN+w6MtKWfgrA7bxJRjB7VlTmwl68jAu2JbO5beoiWKr7sP/K2kitarxzXNPDtpNL9xKg== X-Received: by 2002:a63:4754:: with SMTP id w20mr452063pgk.255.1591875870670; Thu, 11 Jun 2020 04:44:30 -0700 (PDT) Received: from nagraj.local ([49.206.21.239]) by smtp.gmail.com with ESMTPSA id z144sm3088543pfc.195.2020.06.11.04.44.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2020 04:44:29 -0700 (PDT) From: Sumit Semwal To: linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org Cc: Chenbo Feng , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, Charan Teja Reddy , Sumit Semwal , syzbot+3643a18836bce555bff6@syzkaller.appspotmail.com, stable@vger.kernel.org, Arnd Bergmann Subject: [PATCH v2] dma-buf: Move dma_buf_release() from fops to dentry_ops Date: Thu, 11 Jun 2020 17:14:18 +0530 Message-Id: <20200611114418.19852-1-sumit.semwal@linaro.org> X-Mailer: git-send-email 2.27.0 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 Charan Teja reported a 'use-after-free' in dmabuffs_dname [1], which happens if the dma_buf_release() is called while the userspace is accessing the dma_buf pseudo fs's dmabuffs_dname() in another process, and dma_buf_release() releases the dmabuf object when the last reference to the struct file goes away. I discussed with Arnd Bergmann, and he suggested that rather than tying the dma_buf_release() to the file_operations' release(), we can tie it to the dentry_operations' d_release(), which will be called when the last ref to the dentry is removed. The path exercised by __fput() calls f_op->release() first, and then calls dput, which eventually calls d_op->d_release(). In the 'normal' case, when no userspace access is happening via dma_buf pseudo fs, there should be exactly one fd, file, dentry and inode, so closing the fd will kill of everything right away. In the presented case, the dentry's d_release() will be called only when the dentry's last ref is released. Therefore, lets move dma_buf_release() from fops->release() to d_ops->d_release() Many thanks to Arnd for his FS insights :) [1]: https://lore.kernel.org/patchwork/patch/1238278/ Fixes: bb2bb9030425 ("dma-buf: add DMA_BUF_SET_NAME ioctls") Reported-by: syzbot+3643a18836bce555bff6@syzkaller.appspotmail.com Cc: [5.3+] Cc: Arnd Bergmann Reported-by: Charan Teja Reddy Reviewed-by: Arnd Bergmann Signed-off-by: Sumit Semwal --- v2: per Arnd: Moved dma_buf_release() above to avoid forward declaration; removed dentry_ops check. --- drivers/dma-buf/dma-buf.c | 54 ++++++++++++++++++--------------------- 1 file changed, 25 insertions(+), 29 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 01ce125f8e8d..412629601ad3 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -54,37 +54,11 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) dentry->d_name.name, ret > 0 ? name : ""); } -static const struct dentry_operations dma_buf_dentry_ops = { - .d_dname = dmabuffs_dname, -}; - -static struct vfsmount *dma_buf_mnt; - -static int dma_buf_fs_init_context(struct fs_context *fc) -{ - struct pseudo_fs_context *ctx; - - ctx = init_pseudo(fc, DMA_BUF_MAGIC); - if (!ctx) - return -ENOMEM; - ctx->dops = &dma_buf_dentry_ops; - return 0; -} - -static struct file_system_type dma_buf_fs_type = { - .name = "dmabuf", - .init_fs_context = dma_buf_fs_init_context, - .kill_sb = kill_anon_super, -}; - -static int dma_buf_release(struct inode *inode, struct file *file) +static void dma_buf_release(struct dentry *dentry) { struct dma_buf *dmabuf; - if (!is_dma_buf_file(file)) - return -EINVAL; - - dmabuf = file->private_data; + dmabuf = dentry->d_fsdata; BUG_ON(dmabuf->vmapping_counter); @@ -110,9 +84,32 @@ static int dma_buf_release(struct inode *inode, struct file *file) module_put(dmabuf->owner); kfree(dmabuf->name); kfree(dmabuf); +} + +static const struct dentry_operations dma_buf_dentry_ops = { + .d_dname = dmabuffs_dname, + .d_release = dma_buf_release, +}; + +static struct vfsmount *dma_buf_mnt; + +static int dma_buf_fs_init_context(struct fs_context *fc) +{ + struct pseudo_fs_context *ctx; + + ctx = init_pseudo(fc, DMA_BUF_MAGIC); + if (!ctx) + return -ENOMEM; + ctx->dops = &dma_buf_dentry_ops; return 0; } +static struct file_system_type dma_buf_fs_type = { + .name = "dmabuf", + .init_fs_context = dma_buf_fs_init_context, + .kill_sb = kill_anon_super, +}; + static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) { struct dma_buf *dmabuf; @@ -412,7 +409,6 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) } static const struct file_operations dma_buf_fops = { - .release = dma_buf_release, .mmap = dma_buf_mmap_internal, .llseek = dma_buf_llseek, .poll = dma_buf_poll, -- 2.27.0