diff options
author | Elena Reshetova | 2017-10-20 12:53:37 +0300 |
---|---|---|
committer | Anna Schumaker | 2017-11-17 13:48:01 -0500 |
commit | 2f62b5aa4814be2c511553fd6afb4d35b6c2503b (patch) | |
tree | cf402bfd8d23ea6dbf02e67a45edd9e49a8822af /fs | |
parent | 194bc1f48100a3b6fbd50d7a2218b594f0c564b6 (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>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/nfs/inode.c | 12 |
1 files changed, 6 insertions, 6 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); |