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authorAl Viro <viro@zeniv.linux.org.uk>2013-04-03 19:57:00 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2013-04-09 15:16:51 -0400
commitca469f35a8e9ef12571a4b80ac6d7fdc0260fb44 (patch)
tree228daeec1f54db72c32d64bf8b54413c65d0ab30 /fs/proc
parent866ad9a747bbf5461739fcae6d0a41c8971bbe1d (diff)
deal with races between remove_proc_entry() and proc_reg_release()
* serialize the call of ->release() on per-pdeo mutex * don't remove pdeo from per-pde list until we are through with it Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/inode.c85
-rw-r--r--fs/proc/internal.h2
2 files changed, 34 insertions, 53 deletions
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 0cd9d80f28e8..b5b204d6b07f 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -156,6 +156,29 @@ static void unuse_pde(struct proc_dir_entry *pde)
spin_unlock(&pde->pde_unload_lock);
}
+/* pde is locked */
+static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
+{
+ pdeo->count++;
+ if (!mutex_trylock(&pdeo->mutex)) {
+ /* somebody else is doing that, just wait */
+ spin_unlock(&pde->pde_unload_lock);
+ mutex_lock(&pdeo->mutex);
+ spin_lock(&pde->pde_unload_lock);
+ WARN_ON(!list_empty(&pdeo->lh));
+ } else {
+ struct file *file;
+ spin_unlock(&pde->pde_unload_lock);
+ file = pdeo->file;
+ pde->proc_fops->release(file_inode(file), file);
+ spin_lock(&pde->pde_unload_lock);
+ list_del_init(&pdeo->lh);
+ }
+ mutex_unlock(&pdeo->mutex);
+ if (!--pdeo->count)
+ kfree(pdeo);
+}
+
void proc_entry_rundown(struct proc_dir_entry *de)
{
spin_lock(&de->pde_unload_lock);
@@ -173,15 +196,8 @@ void proc_entry_rundown(struct proc_dir_entry *de)
while (!list_empty(&de->pde_openers)) {
struct pde_opener *pdeo;
- struct file *file;
-
pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
- list_del(&pdeo->lh);
- spin_unlock(&de->pde_unload_lock);
- file = pdeo->file;
- de->proc_fops->release(file_inode(file), file);
- kfree(pdeo);
- spin_lock(&de->pde_unload_lock);
+ close_pdeo(de, pdeo);
}
spin_unlock(&de->pde_unload_lock);
}
@@ -357,6 +373,8 @@ static int proc_reg_open(struct inode *inode, struct file *file)
spin_lock(&pde->pde_unload_lock);
if (rv == 0 && release) {
/* To know what to release. */
+ mutex_init(&pdeo->mutex);
+ pdeo->count = 0;
pdeo->file = file;
/* Strictly for "too late" ->release in proc_reg_release(). */
list_add(&pdeo->lh, &pde->pde_openers);
@@ -367,58 +385,19 @@ static int proc_reg_open(struct inode *inode, struct file *file)
return rv;
}
-static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
- struct file *file)
-{
- struct pde_opener *pdeo;
-
- list_for_each_entry(pdeo, &pde->pde_openers, lh) {
- if (pdeo->file == file)
- return pdeo;
- }
- return NULL;
-}
-
static int proc_reg_release(struct inode *inode, struct file *file)
{
struct proc_dir_entry *pde = PDE(inode);
- int rv = 0;
- int (*release)(struct inode *, struct file *);
struct pde_opener *pdeo;
-
spin_lock(&pde->pde_unload_lock);
- pdeo = find_pde_opener(pde, file);
- if (pde->pde_users < 0) {
- /*
- * Can't simply exit, __fput() will think that everything is OK,
- * and move on to freeing struct file. remove_proc_entry() will
- * find slacker in opener's list and will try to do non-trivial
- * things with struct file. Therefore, remove opener from list.
- *
- * But if opener is removed from list, who will ->release it?
- */
- if (pdeo) {
- list_del(&pdeo->lh);
- spin_unlock(&pde->pde_unload_lock);
- rv = pde->proc_fops->release(inode, file);
- kfree(pdeo);
- } else
- spin_unlock(&pde->pde_unload_lock);
- return rv;
- }
- pde->pde_users++;
- release = pde->proc_fops->release;
- if (pdeo) {
- list_del(&pdeo->lh);
- kfree(pdeo);
+ list_for_each_entry(pdeo, &pde->pde_openers, lh) {
+ if (pdeo->file == file) {
+ close_pdeo(pde, pdeo);
+ break;
+ }
}
spin_unlock(&pde->pde_unload_lock);
-
- if (release)
- rv = release(inode, file);
-
- unuse_pde(pde);
- return rv;
+ return 0;
}
static const struct file_operations proc_reg_file_ops = {
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index c43d536f93b9..e2fa9345a9a8 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -153,6 +153,8 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
struct pde_opener {
struct file *file;
struct list_head lh;
+ int count; /* number of threads in close_pdeo() */
+ struct mutex mutex;
};
ssize_t __proc_file_read(struct file *, char __user *, size_t, loff_t *);