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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 12:53:30 +0300
committerJ. Bruce Fields <bfields@redhat.com>2017-11-07 16:43:59 -0500
commit818a34eb266449b1c89242596039a5e44c9be04c (patch)
tree7c9affb6d729a990155f33db99d6e31090aa88d6 /fs/nfsd/nfs4state.c
parentcff7cb2ece397760195ff8a5fc6bf3c860810246 (diff)
fs, nfsd: convert nfs4_file.fi_ref 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_file.fi_ref 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 3f10a397e5ba..e905bf642a53 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -359,7 +359,7 @@ put_nfs4_file(struct nfs4_file *fi)
{
might_lock(&state_lock);
- if (atomic_dec_and_lock(&fi->fi_ref, &state_lock)) {
+ if (refcount_dec_and_lock(&fi->fi_ref, &state_lock)) {
hlist_del_rcu(&fi->fi_hash);
spin_unlock(&state_lock);
WARN_ON_ONCE(!list_empty(&fi->fi_clnt_odstate));
@@ -3401,7 +3401,7 @@ static void nfsd4_init_file(struct knfsd_fh *fh, unsigned int hashval,
{
lockdep_assert_held(&state_lock);
- atomic_set(&fp->fi_ref, 1);
+ refcount_set(&fp->fi_ref, 1);
spin_lock_init(&fp->fi_lock);
INIT_LIST_HEAD(&fp->fi_stateids);
INIT_LIST_HEAD(&fp->fi_delegations);
@@ -3697,7 +3697,7 @@ find_file_locked(struct knfsd_fh *fh, unsigned int hashval)
hlist_for_each_entry_rcu(fp, &file_hashtbl[hashval], fi_hash) {
if (fh_match(&fp->fi_fhandle, fh)) {
- if (atomic_inc_not_zero(&fp->fi_ref))
+ if (refcount_inc_not_zero(&fp->fi_ref))
return fp;
}
}