Commit 3dec7f59 authored by Alexey Dobriyan's avatar Alexey Dobriyan
Browse files

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: default avatarAlexey Dobriyan <adobriyan@gmail.com>
parent 09729a99

fs/proc/generic.c

+38 −10
Original line number Diff line number Diff line
@@ -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;

	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);

	ssize_t rv = -EIO;



	dp = PDE(inode);



	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);

		rv = pde->write_proc(file, buffer, count, pde->data);

		pde_users_dec(pde);

	}

	return rv;

}

fs/proc/inode.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

fs/proc/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -91,3 +91,4 @@ struct pde_opener { 
	int (*release)(struct inode *, struct file *);

	struct list_head lh;

};

void pde_users_dec(struct proc_dir_entry *pde);

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