atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.
The variable nfs_lock_context.count is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
static void nfs_init_lock_context(struct nfs_lock_context *l_ctx)
{
static void nfs_init_lock_context(struct nfs_lock_context *l_ctx)
{
- atomic_set(&l_ctx->count, 1);
+ refcount_set(&l_ctx->count, 1);
l_ctx->lockowner = current->files;
INIT_LIST_HEAD(&l_ctx->list);
atomic_set(&l_ctx->io_count, 0);
l_ctx->lockowner = current->files;
INIT_LIST_HEAD(&l_ctx->list);
atomic_set(&l_ctx->io_count, 0);
do {
if (pos->lockowner != current->files)
continue;
do {
if (pos->lockowner != current->files)
continue;
- atomic_inc(&pos->count);
+ refcount_inc(&pos->count);
return pos;
} while ((pos = list_entry(pos->list.next, typeof(*pos), list)) != head);
return NULL;
return pos;
} while ((pos = list_entry(pos->list.next, typeof(*pos), list)) != head);
return NULL;
struct nfs_open_context *ctx = l_ctx->open_context;
struct inode *inode = d_inode(ctx->dentry);
struct nfs_open_context *ctx = l_ctx->open_context;
struct inode *inode = d_inode(ctx->dentry);
- if (!atomic_dec_and_lock(&l_ctx->count, &inode->i_lock))
+ if (!refcount_dec_and_lock(&l_ctx->count, &inode->i_lock))
return;
list_del(&l_ctx->list);
spin_unlock(&inode->i_lock);
return;
list_del(&l_ctx->list);
spin_unlock(&inode->i_lock);
struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx)
{
if (ctx != NULL)
struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx)
{
if (ctx != NULL)
- atomic_inc(&ctx->lock_context.count);
+ refcount_inc(&ctx->lock_context.count);
return ctx;
}
EXPORT_SYMBOL_GPL(get_nfs_open_context);
return ctx;
}
EXPORT_SYMBOL_GPL(get_nfs_open_context);
struct super_block *sb = ctx->dentry->d_sb;
if (!list_empty(&ctx->list)) {
struct super_block *sb = ctx->dentry->d_sb;
if (!list_empty(&ctx->list)) {
- if (!atomic_dec_and_lock(&ctx->lock_context.count, &inode->i_lock))
+ if (!refcount_dec_and_lock(&ctx->lock_context.count, &inode->i_lock))
return;
list_del(&ctx->list);
spin_unlock(&inode->i_lock);
return;
list_del(&ctx->list);
spin_unlock(&inode->i_lock);
- } else if (!atomic_dec_and_test(&ctx->lock_context.count))
+ } else if (!refcount_dec_and_test(&ctx->lock_context.count))
return;
if (inode != NULL)
NFS_PROTO(inode)->close_context(ctx, is_sync);
return;
if (inode != NULL)
NFS_PROTO(inode)->close_context(ctx, is_sync);
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/rbtree.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/rbtree.h>
+#include <linux/refcount.h>
#include <linux/rwsem.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#include <linux/wait.h>
};
struct nfs_lock_context {
};
struct nfs_lock_context {
struct list_head list;
struct nfs_open_context *open_context;
fl_owner_t lockowner;
struct list_head list;
struct nfs_open_context *open_context;
fl_owner_t lockowner;