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proc 1/2: do PDE usecounting even for ->read_proc, ->write_proc

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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>
This commit is contained in:
Alexey Dobriyan 2009-02-20 17:04:33 +03:00
parent 09729a9919
commit 3dec7f59c3
3 changed files with 39 additions and 10 deletions
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46
fs/proc/generic.c
View File

@ -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);
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;
}

2
fs/proc/inode.c
View File

@ -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);

1
fs/proc/internal.h
View File

@ -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);