From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754116AbZAZX0Y (ORCPT ); Mon, 26 Jan 2009 18:26:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751875AbZAZX0Q (ORCPT ); Mon, 26 Jan 2009 18:26:16 -0500 Received: from fg-out-1718.google.com ([72.14.220.158]:29094 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751665AbZAZX0P (ORCPT ); Mon, 26 Jan 2009 18:26:15 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:mime-version:content-type :content-disposition:user-agent; b=iYqKcEVmHlG2zPC9CDxlUEji2ZrMCVaJHyuKBfM7mV65NPpxagm0N68QE8RkaXXF4/ y2/z/o+Tqlq1iTKAWqZDd+Xv0sS5aDoggcTYQwxSk2VKAdLaG/Mxl3avNutDsie3pv/w yGrg+9+VNdUvWExeibZZBqgudaAr/yCGFMy6c= Date: Tue, 27 Jan 2009 02:31:51 +0300 From: Alexey Dobriyan To: jlayton@redhat.com, viro@zeniv.linux.org.uk Cc: linux-kernel@vger.kernel.org Subject: [PATCH 1/2] proc: do PDE usecounting even for ->read_proc, ->write_proc Message-ID: <20090126233151.GA7339@x200.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Not exactly tested but one should get the idea. ----------------------------------------------- struct proc_dir_entry::owner is going to be removed. Now it's only necessary to protect PDEs which are using ->read_proc, ->write_proc hooks. However, ->owner assignments are racy and make it very easy for someone to switch ->owner on live PDE (as some subsystems do) without fixing refcounts and so on. http://bugzilla.kernel.org/show_bug.cgi?id=12454 So, ->owner is on death row. Proxy file operations exist already (proc_file_operations), just bump usecount when necessary. Signed-off-by: Alexey Dobriyan --- fs/proc/generic.c | 48 ++++++++++++++++++++++++++++++++++++++---------- fs/proc/inode.c | 2 +- fs/proc/internal.h | 1 + 3 files changed, 40 insertions(+), 11 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 5ee636a..65cc1ee 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -37,7 +37,7 @@ static int proc_match(int len, const char *name, struct proc_dir_entry *de) #define PROC_BLOCK_SIZE (PAGE_SIZE - 1024) static ssize_t -proc_file_read(struct file *file, char __user *buf, size_t nbytes, +__proc_file_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { struct inode * inode = file->f_path.dentry->d_inode; @@ -183,19 +183,47 @@ proc_file_read(struct file *file, char __user *buf, size_t nbytes, } static ssize_t +proc_file_read(struct file *file, char __user *buf, size_t nbytes, + loff_t *ppos) +{ + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + ssize_t rv = -EIO; + + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + spin_unlock(&pde->pde_unload_lock); + + rv = __proc_file_read(file, buf, nbytes, ppos); + + pde_users_dec(pde); + return rv; +} + +static ssize_t proc_file_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos) { - struct inode *inode = file->f_path.dentry->d_inode; - struct proc_dir_entry * dp; - - dp = PDE(inode); - - if (!dp->write_proc) - return -EIO; + struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode); + ssize_t rv = -EIO; + + if (pde->write_proc) { + spin_lock(&pde->pde_unload_lock); + if (!pde->proc_fops) { + spin_unlock(&pde->pde_unload_lock); + return rv; + } + pde->pde_users++; + spin_unlock(&pde->pde_unload_lock); - /* FIXME: does this routine need ppos? probably... */ - return dp->write_proc(file, buffer, count, dp->data); + /* FIXME: does this routine need ppos? probably... */ + rv = pde->write_proc(file, buffer, count, pde->data); + pde_users_dec(pde); + } + return rv; } diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 0bbb937..7a55346 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -127,7 +127,7 @@ static void __pde_users_dec(struct proc_dir_entry *pde) complete(pde->pde_unload_completion); } -static void pde_users_dec(struct proc_dir_entry *pde) +void pde_users_dec(struct proc_dir_entry *pde) { spin_lock(&pde->pde_unload_lock); __pde_users_dec(pde); diff --git a/fs/proc/internal.h b/fs/proc/internal.h index ab62ede..5b890ba 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -102,5 +102,6 @@ struct pde_opener { int (*release)(struct inode *, struct file *); struct list_head lh; }; +void pde_users_dec(struct proc_dir_entry *pde); extern struct list_head proc_automounts; -- 1.5.6.5