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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 12:53:37 +0300
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2017-11-17 13:48:01 -0500
commit2f62b5aa4814be2c511553fd6afb4d35b6c2503b (patch)
treecf402bfd8d23ea6dbf02e67a45edd9e49a8822af
parent194bc1f48100a3b6fbd50d7a2218b594f0c564b6 (diff)
fs, nfs: convert nfs_lock_context.count from atomic_t to refcount_t
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>
-rw-r--r--fs/nfs/inode.c12
-rw-r--r--include/linux/nfs_fs.h3
2 files changed, 8 insertions, 7 deletions
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 134d9f560240..52a60e399a2d 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -783,7 +783,7 @@ EXPORT_SYMBOL_GPL(nfs_getattr);
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);
@@ -797,7 +797,7 @@ static struct nfs_lock_context *__nfs_find_lock_context(struct nfs_open_context
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;
@@ -836,7 +836,7 @@ void nfs_put_lock_context(struct nfs_lock_context *l_ctx)
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);
@@ -913,7 +913,7 @@ EXPORT_SYMBOL_GPL(alloc_nfs_open_context);
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);
@@ -924,11 +924,11 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
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);
- } 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);
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 453f491a5fda..e6706913e6c2 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -22,6 +22,7 @@
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/rbtree.h>
+#include <linux/refcount.h>
#include <linux/rwsem.h>
#include <linux/wait.h>
@@ -55,7 +56,7 @@ struct nfs_access_entry {
};
struct nfs_lock_context {
- atomic_t count;
+ refcount_t count;
struct list_head list;
struct nfs_open_context *open_context;
fl_owner_t lockowner;