From patchwork Fri May 8 06:41:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Charan Teja Kalla X-Patchwork-Id: 11535739 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0DB0D92A for ; Fri, 8 May 2020 06:41:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E3BFD21582 for ; Fri, 8 May 2020 06:41:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="FiFPWwcm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726771AbgEHGl2 (ORCPT ); Fri, 8 May 2020 02:41:28 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:16515 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725988AbgEHGl2 (ORCPT ); Fri, 8 May 2020 02:41:28 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1588920086; h=Message-Id: Date: Subject: Cc: To: From: Sender; bh=JGbArbE31FgJMYaWjsdsGR2edFKZOM0SJ0pUFigb4cY=; b=FiFPWwcmOG9v5Rx3r3YH2gzQuQoo9wu5zS+dj/jk2kK36PDELbhEz86E/9wh+agsjRD7p64Q Q6mXqvvL4LpnJ86W8El9RAxizDwunlgIj5UTSU2nQ/DgeNC/JLTHImapzD90ZYUsPnGGlVBz a1gpevOJHn+QWtl9ZilbpcJlRQA= X-Mailgun-Sending-Ip: 104.130.122.26 X-Mailgun-Sid: WyI3ZjU0NiIsICJsaW51eC1tZWRpYUB2Z2VyLmtlcm5lbC5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5eb4ff0b.7fbb7575f688-smtp-out-n04; Fri, 08 May 2020 06:41:15 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id BEBCCC4478C; Fri, 8 May 2020 06:41:15 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-caf-mail-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=2.0 tests=ALL_TRUSTED,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.0 Received: from charante-linux.qualcomm.com (blr-c-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: charante) by smtp.codeaurora.org (Postfix) with ESMTPSA id A2B60C433BA; Fri, 8 May 2020 06:41:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org A2B60C433BA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=charante@codeaurora.org From: Charan Teja Reddy To: sumit.semwal@linaro.org, ghackmann@google.com, fengc@google.com Cc: linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, Charan Teja Reddy , Subject: [PATCH v2] dma-buf: fix use-after-free in dmabuffs_dname Date: Fri, 8 May 2020 12:11:03 +0530 Message-Id: <1588920063-17624-1-git-send-email-charante@codeaurora.org> X-Mailer: git-send-email 1.9.1 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org The following race occurs while accessing the dmabuf object exported as file: P1 P2 dma_buf_release() dmabuffs_dname() [say lsof reading /proc//fd/] read dmabuf stored in dentry->d_fsdata Free the dmabuf object Start accessing the dmabuf structure In the above description, the dmabuf object freed in P1 is being accessed from P2 which is resulting into the use-after-free. Below is the dump stack reported. We are reading the dmabuf object stored in the dentry->d_fsdata but there is no binding between the dentry and the dmabuf which means that the dmabuf can be freed while it is being read from ->d_fsdata and inuse. Reviews on the patch V1 says that protecting the dmabuf inuse with an extra refcount is not a viable solution as the exported dmabuf is already under file's refcount and keeping the multiple refcounts on the same object coordinated is not possible. As we are reading the dmabuf in ->d_fsdata just to get the user passed name, we can directly store the name in d_fsdata thus can avoid the reading of dmabuf altogether. Call Trace: kasan_report+0x12/0x20 __asan_report_load8_noabort+0x14/0x20 dmabuffs_dname+0x4f4/0x560 tomoyo_realpath_from_path+0x165/0x660 tomoyo_get_realpath tomoyo_check_open_permission+0x2a3/0x3e0 tomoyo_file_open tomoyo_file_open+0xa9/0xd0 security_file_open+0x71/0x300 do_dentry_open+0x37a/0x1380 vfs_open+0xa0/0xd0 path_openat+0x12ee/0x3490 do_filp_open+0x192/0x260 do_sys_openat2+0x5eb/0x7e0 do_sys_open+0xf2/0x180 Fixes: bb2bb9030425 ("dma-buf: add DMA_BUF_SET_NAME ioctls") Reported-by: syzbot+3643a18836bce555bff6@syzkaller.appspotmail.com Cc: [5.3+] Signed-off-by: Charan Teja Reddy --- Changes in v2: - Pass the user passed name in ->d_fsdata instead of dmabuf - Improve the commit message Changes in v1: (https://patchwork.kernel.org/patch/11514063/) drivers/dma-buf/dma-buf.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 01ce125..0071f7d 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -40,15 +41,13 @@ struct dma_buf_list { static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) { - struct dma_buf *dmabuf; char name[DMA_BUF_NAME_LEN]; size_t ret = 0; - dmabuf = dentry->d_fsdata; - dma_resv_lock(dmabuf->resv, NULL); - if (dmabuf->name) - ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN); - dma_resv_unlock(dmabuf->resv); + spin_lock(&dentry->d_lock); + if (dentry->d_fsdata) + ret = strlcpy(name, dentry->d_fsdata, DMA_BUF_NAME_LEN); + spin_unlock(&dentry->d_lock); return dynamic_dname(dentry, buffer, buflen, "/%s:%s", dentry->d_name.name, ret > 0 ? name : ""); @@ -80,12 +79,16 @@ static int dma_buf_fs_init_context(struct fs_context *fc) static int dma_buf_release(struct inode *inode, struct file *file) { struct dma_buf *dmabuf; + struct dentry *dentry = file->f_path.dentry; if (!is_dma_buf_file(file)) return -EINVAL; dmabuf = file->private_data; + spin_lock(&dentry->d_lock); + dentry->d_fsdata = NULL; + spin_unlock(&dentry->d_lock); BUG_ON(dmabuf->vmapping_counter); /* @@ -343,6 +346,7 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) } kfree(dmabuf->name); dmabuf->name = name; + dmabuf->file->f_path.dentry->d_fsdata = name; out_unlock: dma_resv_unlock(dmabuf->resv); @@ -446,7 +450,6 @@ static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags) goto err_alloc_file; file->f_flags = flags & (O_ACCMODE | O_NONBLOCK); file->private_data = dmabuf; - file->f_path.dentry->d_fsdata = dmabuf; return file;