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NFS: Fix up nfs_ctx_key_to_expire()

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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@hammerspace.com>
This commit is contained in:
Trond Myklebust 2021-07-10 18:07:14 -04:00
parent 9019fb391d
commit ca05cbae2a
3 changed files with 31 additions and 16 deletions
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4
fs/nfs/inode.c
View file

@ -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);
}

41
fs/nfs/write.c
View file

@ -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;
}
/*

2
include/linux/nfs_fs.h
View file

@ -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;