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 <adobriyan@gmail.com>
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 8c68bbe..fa678ab 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -37,7 +37,7 @@
#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 @@
}
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);
+ struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
+ ssize_t rv = -EIO;
- if (!dp->write_proc)
- return -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;
}