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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 12:53:29 +0300
committerJ. Bruce Fields <bfields@redhat.com>2017-11-07 16:43:59 -0500
commitcff7cb2ece397760195ff8a5fc6bf3c860810246 (patch)
tree7d253b4fc7b44d2f1b2f0e9aa7715fad8479ae0e /fs/nfsd/nfs4state.c
parenta15dfcd529ab43265e70ec32d3b9d2286872d412 (diff)
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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>
Diffstat (limited to 'fs/nfsd/nfs4state.c')
-rw-r--r--fs/nfsd/nfs4state.c6
1 files changed, 3 insertions, 3 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);