From patchwork Mon Jan 11 13:01:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 360957 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, 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 05649C433E0 for ; Mon, 11 Jan 2021 13:53:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2119222B3 for ; Mon, 11 Jan 2021 13:53:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729197AbhAKNIf (ORCPT ); Mon, 11 Jan 2021 08:08:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:55720 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731004AbhAKNIW (ORCPT ); Mon, 11 Jan 2021 08:08:22 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8CFFE225AB; Mon, 11 Jan 2021 13:07:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610370462; bh=ctz+HUrC3mHkW7PxvILZIdjn4dG5FDl8YWBYehaPlV8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y8BNZt3bXpkJflUzVwVw0chu2Fof80MpWbjLkAUcCvB8Q89oqLyTkTAHQHuVT/Z+r jBtljo23N31306UX3Zsa8LKhNBkZo+EoWxKfCcdcL4TpOt8o0xKJQAWqiZzpjVY9jK QOcZzRMCjyeN5Y4WyLsA0+mULxuoawGG2n351b0U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexey Dobriyan , Al Viro , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.19 09/77] proc: change ->nlink under proc_subdir_lock Date: Mon, 11 Jan 2021 14:01:18 +0100 Message-Id: <20210111130036.858266032@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210111130036.414620026@linuxfoundation.org> References: <20210111130036.414620026@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Alexey Dobriyan [ Upstream commit e06689bf57017ac022ccf0f2a5071f760821ce0f ] Currently gluing PDE into global /proc tree is done under lock, but changing ->nlink is not. Additionally struct proc_dir_entry::nlink is not atomic so updates can be lost. Link: http://lkml.kernel.org/r/20190925202436.GA17388@avx2 Signed-off-by: Alexey Dobriyan Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/proc/generic.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index e39bac94dead0..7820fe524cb03 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -137,8 +137,12 @@ static int proc_getattr(const struct path *path, struct kstat *stat, { struct inode *inode = d_inode(path->dentry); struct proc_dir_entry *de = PDE(inode); - if (de && de->nlink) - set_nlink(inode, de->nlink); + if (de) { + nlink_t nlink = READ_ONCE(de->nlink); + if (nlink > 0) { + set_nlink(inode, nlink); + } + } generic_fillattr(inode, stat); return 0; @@ -361,6 +365,7 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir, write_unlock(&proc_subdir_lock); goto out_free_inum; } + dir->nlink++; write_unlock(&proc_subdir_lock); return dp; @@ -471,10 +476,7 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode, ent->data = data; ent->proc_fops = &proc_dir_operations; ent->proc_iops = &proc_dir_inode_operations; - parent->nlink++; ent = proc_register(parent, ent); - if (!ent) - parent->nlink--; } return ent; } @@ -504,10 +506,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name) ent->data = NULL; ent->proc_fops = NULL; ent->proc_iops = NULL; - parent->nlink++; ent = proc_register(parent, ent); - if (!ent) - parent->nlink--; } return ent; } @@ -665,8 +664,12 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) len = strlen(fn); de = pde_subdir_find(parent, fn, len); - if (de) + if (de) { rb_erase(&de->subdir_node, &parent->subdir); + if (S_ISDIR(de->mode)) { + parent->nlink--; + } + } write_unlock(&proc_subdir_lock); if (!de) { WARN(1, "name '%s'\n", name); @@ -675,9 +678,6 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) proc_entry_rundown(de); - if (S_ISDIR(de->mode)) - parent->nlink--; - de->nlink = 0; WARN(pde_subdir_first(de), "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n", __func__, de->parent->name, de->name, pde_subdir_first(de)->name); @@ -713,13 +713,12 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) de = next; continue; } - write_unlock(&proc_subdir_lock); - - proc_entry_rundown(de); next = de->parent; if (S_ISDIR(de->mode)) next->nlink--; - de->nlink = 0; + write_unlock(&proc_subdir_lock); + + proc_entry_rundown(de); if (de == root) break; pde_put(de);