diff options
| author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 12:53:29 +0300 |
|---|---|---|
| committer | J. Bruce Fields <bfields@redhat.com> | 2017-11-07 16:43:59 -0500 |
| commit | cff7cb2ece397760195ff8a5fc6bf3c860810246 (patch) | |
| tree | 7d253b4fc7b44d2f1b2f0e9aa7715fad8479ae0e | |
| parent | a15dfcd529ab43265e70ec32d3b9d2286872d412 (diff) | |
fs, nfsd: convert nfs4_cntl_odstate.co_odcount 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 nfs4_cntl_odstate.co_odcount 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: J. Bruce Fields <bfields@redhat.com>
| -rw-r--r-- | fs/nfsd/nfs4state.c | 6 | ||||
| -rw-r--r-- | fs/nfsd/state.h | 2 |
2 files changed, 4 insertions, 4 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index df2e5b4b222e..3f10a397e5ba 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -568,7 +568,7 @@ alloc_clnt_odstate(struct nfs4_client *clp) co = kmem_cache_zalloc(odstate_slab, GFP_KERNEL); if (co) { co->co_client = clp; - atomic_set(&co->co_odcount, 1); + refcount_set(&co->co_odcount, 1); } return co; } @@ -586,7 +586,7 @@ static inline void get_clnt_odstate(struct nfs4_clnt_odstate *co) { if (co) - atomic_inc(&co->co_odcount); + refcount_inc(&co->co_odcount); } static void @@ -598,7 +598,7 @@ put_clnt_odstate(struct nfs4_clnt_odstate *co) return; fp = co->co_file; - if (atomic_dec_and_lock(&co->co_odcount, &fp->fi_lock)) { + if (refcount_dec_and_lock(&co->co_odcount, &fp->fi_lock)) { list_del(&co->co_perfile); spin_unlock(&fp->fi_lock); diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index c259271c35a4..2ed368a91a10 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -468,7 +468,7 @@ struct nfs4_clnt_odstate { struct nfs4_client *co_client; struct nfs4_file *co_file; struct list_head co_perfile; - atomic_t co_odcount; + refcount_t co_odcount; }; /* |