From patchwork Thu Jun 11 13:39:55 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: 11600127 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 432B0138C for ; Thu, 11 Jun 2020 13:40:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24C5E20801 for ; Thu, 11 Jun 2020 13:40:25 +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="Uil+NTUp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728022AbgFKNkV (ORCPT ); Thu, 11 Jun 2020 09:40:21 -0400 Received: from mail27.static.mailgun.info ([104.130.122.27]:35757 "EHLO mail27.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727088AbgFKNkR (ORCPT ); Thu, 11 Jun 2020 09:40:17 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1591882816; h=Content-Transfer-Encoding: Content-Type: MIME-Version: Date: Message-ID: Subject: From: Cc: To: Sender; bh=ihrRcjhW9ULLbY+ZlVGkZ/PVZKfJ2usDc73eH+pAOvY=; b=Uil+NTUpKOOa8nHeFTQGndl9UYMGYq0aO//iuzg9Dqp1aJFFwVacouPcjpXu+X63caDWdBGH oG4WRQzH98UXzWFdyBoM5eU85OcG81b7uu4u1qUi73owWB6tnRktjIna8icxQ2Ed/mjwJ0KU DFEWv0waW36LpkwKEVi3kw7h0tE= X-Mailgun-Sending-Ip: 104.130.122.27 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 smtp-out-n01.prod.us-east-1.postgun.com with SMTP id 5ee23432c76a4e7a2a8f8d32 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 11 Jun 2020 13:40:02 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 702DCC43387; Thu, 11 Jun 2020 13:40:01 +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 [192.168.1.102] (unknown [183.83.143.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: charante) by smtp.codeaurora.org (Postfix) with ESMTPSA id 823FBC433CA; Thu, 11 Jun 2020 13:39:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 823FBC433CA 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 To: Sumit Semwal , "open list:DMA BUFFER SHARING FRAMEWORK" , DRI mailing list Cc: Linaro MM SIG , LKML , vinmenon@codeaurora.org, stable@vger.kernel.org From: Charan Teja Kalla Subject: [PATCH] dmabuf: use spinlock to access dmabuf->name Message-ID: <316a5cf9-ca71-6506-bf8b-e79ded9055b2@codeaurora.org> Date: Thu, 11 Jun 2020 19:09:55 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 Content-Language: en-US Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org There exists a sleep-while-atomic bug while accessing the dmabuf->name under mutex in the dmabuffs_dname(). This is caused from the SELinux permissions checks on a process where it tries to validate the inherited files from fork() by traversing them through iterate_fd() (which traverse files under spin_lock) and call match_file(security/selinux/hooks.c) where the permission checks happen. This audit information is logged using dump_common_audit_data() where it calls d_path() to get the file path name. If the file check happen on the dmabuf's fd, then it ends up in ->dmabuffs_dname() and use mutex to access dmabuf->name. The flow will be like below: flush_unauthorized_files() iterate_fd() spin_lock() --> Start of the atomic section. match_file() file_has_perm() avc_has_perm() avc_audit() slow_avc_audit() common_lsm_audit() dump_common_audit_data() audit_log_d_path() d_path() dmabuffs_dname() mutex_lock()--> Sleep while atomic. Call trace captured (on 4.19 kernels) is below: ___might_sleep+0x204/0x208 __might_sleep+0x50/0x88 __mutex_lock_common+0x5c/0x1068 __mutex_lock_common+0x5c/0x1068 mutex_lock_nested+0x40/0x50 dmabuffs_dname+0xa0/0x170 d_path+0x84/0x290 audit_log_d_path+0x74/0x130 common_lsm_audit+0x334/0x6e8 slow_avc_audit+0xb8/0xf8 avc_has_perm+0x154/0x218 file_has_perm+0x70/0x180 match_file+0x60/0x78 iterate_fd+0x128/0x168 selinux_bprm_committing_creds+0x178/0x248 security_bprm_committing_creds+0x30/0x48 install_exec_creds+0x1c/0x68 load_elf_binary+0x3a4/0x14e0 search_binary_handler+0xb0/0x1e0 So, use spinlock to access dmabuf->name to avoid sleep-while-atomic. Cc: [5.3+] Signed-off-by: Charan Teja Reddy --- drivers/dma-buf/dma-buf.c | 13 +++++++------ include/linux/dma-buf.h | 1 + 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 01ce125..2e0456c 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -45,10 +45,10 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) size_t ret = 0; dmabuf = dentry->d_fsdata; - dma_resv_lock(dmabuf->resv, NULL); + spin_lock(&dmabuf->name_lock); if (dmabuf->name) ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN); - dma_resv_unlock(dmabuf->resv); + spin_unlock(&dmabuf->name_lock); return dynamic_dname(dentry, buffer, buflen, "/%s:%s", dentry->d_name.name, ret > 0 ? name : ""); @@ -335,7 +335,7 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) if (IS_ERR(name)) return PTR_ERR(name); - dma_resv_lock(dmabuf->resv, NULL); + spin_lock(&dmabuf->name_lock); if (!list_empty(&dmabuf->attachments)) { ret = -EBUSY; kfree(name); @@ -345,7 +345,7 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) dmabuf->name = name; out_unlock: - dma_resv_unlock(dmabuf->resv); + spin_unlock(&dmabuf->name_lock); return ret; } @@ -405,10 +405,10 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) /* Don't count the temporary reference taken inside procfs seq_show */ seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1); seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name); - dma_resv_lock(dmabuf->resv, NULL); + spin_lock(&dmabuf->name_lock); if (dmabuf->name) seq_printf(m, "name:\t%s\n", dmabuf->name); - dma_resv_unlock(dmabuf->resv); + spin_unlock(&dmabuf->name_lock); } static const struct file_operations dma_buf_fops = { @@ -546,6 +546,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) dmabuf->size = exp_info->size; dmabuf->exp_name = exp_info->exp_name; dmabuf->owner = exp_info->owner; + spin_lock_init(&dmabuf->name_lock); init_waitqueue_head(&dmabuf->poll); dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll; dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0; diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index ab0c156..93108fd 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -311,6 +311,7 @@ struct dma_buf { void *vmap_ptr; const char *exp_name; const char *name; + spinlock_t name_lock; struct module *owner; struct list_head list_node; void *priv;