From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
[ Upstream commit ca05cbae2a0468e5d78e9b4605936a8bf5da328b ]
If the cached credential exists but doesn't have any expiration callback
then exit early.
Fix up atomicity issues when replacing the credential with a new one
since the existing code could lead to refcount leaks.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/nfs/inode.c | 4 ++--
fs/nfs/write.c | 41 ++++++++++++++++++++++++++++-------------
include/linux/nfs_fs.h | 2 +-
3 files changed, 31 insertions(+), 16 deletions(-)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 853213b3a2095..4f45281c47cfb 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1024,7 +1024,7 @@ struct nfs_open_context *alloc_nfs_open_context(struct dentry *dentry,
ctx->cred = get_cred(filp->f_cred);
else
ctx->cred = get_current_cred();
- ctx->ll_cred = NULL;
+ rcu_assign_pointer(ctx->ll_cred, NULL);
ctx->state = NULL;
ctx->mode = f_mode;
ctx->flags = 0;
@@ -1063,7 +1063,7 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
put_cred(ctx->cred);
dput(ctx->dentry);
nfs_sb_deactive(sb);
- put_rpccred(ctx->ll_cred);
+ put_rpccred(rcu_dereference_protected(ctx->ll_cred, 1));
kfree(ctx->mdsthreshold);
kfree_rcu(ctx, rcu_head);
}
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index eae9bf1140417..773ea2c8504d6 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1246,7 +1246,7 @@ nfs_key_timeout_notify(struct file *filp, struct inode *inode)
struct nfs_open_context *ctx = nfs_file_open_context(filp);
if (nfs_ctx_key_to_expire(ctx, inode) &&
- !ctx->ll_cred)
+ !rcu_access_pointer(ctx->ll_cred))
/* Already expired! */
return -EACCES;
return 0;
@@ -1258,23 +1258,38 @@ nfs_key_timeout_notify(struct file *filp, struct inode *inode)
bool nfs_ctx_key_to_expire(struct nfs_open_context *ctx, struct inode *inode)
{
struct rpc_auth *auth = NFS_SERVER(inode)->client->cl_auth;
- struct rpc_cred *cred = ctx->ll_cred;
+ struct rpc_cred *cred, *new, *old = NULL;
struct auth_cred acred = {
.cred = ctx->cred,
};
+ bool ret = false;
- if (cred && !cred->cr_ops->crmatch(&acred, cred, 0)) {
- put_rpccred(cred);
- ctx->ll_cred = NULL;
- cred = NULL;
- }
- if (!cred)
- cred = auth->au_ops->lookup_cred(auth, &acred, 0);
- if (!cred || IS_ERR(cred))
+ rcu_read_lock();
+ cred = rcu_dereference(ctx->ll_cred);
+ if (cred && !(cred->cr_ops->crkey_timeout &&
+ cred->cr_ops->crkey_timeout(cred)))
+ goto out;
+ rcu_read_unlock();
+
+ new = auth->au_ops->lookup_cred(auth, &acred, 0);
+ if (new == cred) {
+ put_rpccred(new);
return true;
- ctx->ll_cred = cred;
- return !!(cred->cr_ops->crkey_timeout &&
- cred->cr_ops->crkey_timeout(cred));
+ }
+ if (IS_ERR_OR_NULL(new)) {
+ new = NULL;
+ ret = true;
+ } else if (new->cr_ops->crkey_timeout &&
+ new->cr_ops->crkey_timeout(new))
+ ret = true;
+
+ rcu_read_lock();
+ old = rcu_dereference_protected(xchg(&ctx->ll_cred,
+ RCU_INITIALIZER(new)), 1);
+out:
+ rcu_read_unlock();
+ put_rpccred(old);
+ return ret;
}
/*
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index b9a8b925db430..9b75448ce0df8 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -81,7 +81,7 @@ struct nfs_open_context {
fl_owner_t flock_owner;
struct dentry *dentry;
const struct cred *cred;
- struct rpc_cred *ll_cred; /* low-level cred - use to check for expiry */
+ struct rpc_cred __rcu *ll_cred; /* low-level cred - use to check for expiry */
struct nfs4_state *state;
fmode_t mode;
--
2.33.0
