From 3dec7f59c370c7b58184d63293c3dc984d475840 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Fri, 20 Feb 2009 17:04:33 +0300 Subject: proc 1/2: do PDE usecounting even for ->read_proc, ->write_proc 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 ++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 38 insertions(+), 10 deletions(-) (limited to 'fs/proc/generic.c') diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 8c68bbe2b61..fa678abc9db 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; @@ -182,20 +182,48 @@ proc_file_read(struct file *file, char __user *buf, size_t nbytes, return retval; } +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; } -- cgit v1.2.3