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SUNRPC: Fix a lock recursion in the auth_gss downcall
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 When we look up a new cred in the auth_gss downcall so that we can stuff
 the credcache, we do not want that lookup to queue up an upcall in order
 to initialise it. To do an upcall here not only redundant, but since we
 are already holding the inode->i_mutex, it will trigger a lock recursion.

 This patch allows rpcauth cache searches to indicate that they can cope
 with uninitialised credentials.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Trond Myklebust authored and Trond Myklebust committed Feb 1, 2006
1 parent aaaa994 commit 8a31776
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Showing 4 changed files with 37 additions and 16 deletions.
5 changes: 5 additions & 0 deletions include/linux/sunrpc/auth.h
View file
Expand Up @@ -50,6 +50,7 @@ struct rpc_cred {
};
#define RPCAUTH_CRED_LOCKED 0x0001
#define RPCAUTH_CRED_UPTODATE 0x0002
#define RPCAUTH_CRED_NEW 0x0004

#define RPCAUTH_CRED_MAGIC 0x0f4aa4f0

Expand Down Expand Up @@ -87,6 +88,10 @@ struct rpc_auth {
* uid/gid, fs[ug]id, gids)
*/

/* Flags for rpcauth_lookupcred() */
#define RPCAUTH_LOOKUP_NEW 0x01 /* Accept an uninitialised cred */
#define RPCAUTH_LOOKUP_ROOTCREDS 0x02 /* This really ought to go! */

/*
* Client authentication ops
*/
Expand Down
17 changes: 10 additions & 7 deletions net/sunrpc/auth.c
View file
Expand Up @@ -184,7 +184,7 @@ rpcauth_gc_credcache(struct rpc_auth *auth, struct hlist_head *free)
*/
struct rpc_cred *
rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
int taskflags)
int flags)
{
struct rpc_cred_cache *cache = auth->au_credcache;
HLIST_HEAD(free);
Expand All @@ -193,7 +193,7 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
*cred = NULL;
int nr = 0;

if (!(taskflags & RPC_TASK_ROOTCREDS))
if (!(flags & RPCAUTH_LOOKUP_ROOTCREDS))
nr = acred->uid & RPC_CREDCACHE_MASK;
retry:
spin_lock(&rpc_credcache_lock);
Expand All @@ -202,7 +202,7 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
hlist_for_each_safe(pos, next, &cache->hashtable[nr]) {
struct rpc_cred *entry;
entry = hlist_entry(pos, struct rpc_cred, cr_hash);
if (entry->cr_ops->crmatch(acred, entry, taskflags)) {
if (entry->cr_ops->crmatch(acred, entry, flags)) {
hlist_del(&entry->cr_hash);
cred = entry;
break;
Expand All @@ -224,7 +224,7 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
rpcauth_destroy_credlist(&free);

if (!cred) {
new = auth->au_ops->crcreate(auth, acred, taskflags);
new = auth->au_ops->crcreate(auth, acred, flags);
if (!IS_ERR(new)) {
#ifdef RPC_DEBUG
new->cr_magic = RPCAUTH_CRED_MAGIC;
Expand All @@ -238,7 +238,7 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
}

struct rpc_cred *
rpcauth_lookupcred(struct rpc_auth *auth, int taskflags)
rpcauth_lookupcred(struct rpc_auth *auth, int flags)
{
struct auth_cred acred = {
.uid = current->fsuid,
Expand All @@ -250,7 +250,7 @@ rpcauth_lookupcred(struct rpc_auth *auth, int taskflags)
dprintk("RPC: looking up %s cred\n",
auth->au_ops->au_name);
get_group_info(acred.group_info);
ret = auth->au_ops->lookup_cred(auth, &acred, taskflags);
ret = auth->au_ops->lookup_cred(auth, &acred, flags);
put_group_info(acred.group_info);
return ret;
}
Expand All @@ -265,11 +265,14 @@ rpcauth_bindcred(struct rpc_task *task)
.group_info = current->group_info,
};
struct rpc_cred *ret;
int flags = 0;

dprintk("RPC: %4d looking up %s cred\n",
task->tk_pid, task->tk_auth->au_ops->au_name);
get_group_info(acred.group_info);
ret = auth->au_ops->lookup_cred(auth, &acred, task->tk_flags);
if (task->tk_flags & RPC_TASK_ROOTCREDS)
flags |= RPCAUTH_LOOKUP_ROOTCREDS;
ret = auth->au_ops->lookup_cred(auth, &acred, flags);
if (!IS_ERR(ret))
task->tk_msg.rpc_cred = ret;
else
Expand Down
25 changes: 19 additions & 6 deletions net/sunrpc/auth_gss/auth_gss.c
View file
Expand Up @@ -158,6 +158,7 @@ gss_cred_set_ctx(struct rpc_cred *cred, struct gss_cl_ctx *ctx)
old = gss_cred->gc_ctx;
gss_cred->gc_ctx = ctx;
cred->cr_flags |= RPCAUTH_CRED_UPTODATE;
cred->cr_flags &= ~RPCAUTH_CRED_NEW;
write_unlock(&gss_ctx_lock);
if (old)
gss_put_ctx(old);
Expand Down Expand Up @@ -580,7 +581,7 @@ gss_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
} else {
struct auth_cred acred = { .uid = uid };
spin_unlock(&gss_auth->lock);
cred = rpcauth_lookup_credcache(clnt->cl_auth, &acred, 0);
cred = rpcauth_lookup_credcache(clnt->cl_auth, &acred, RPCAUTH_LOOKUP_NEW);
if (IS_ERR(cred)) {
err = PTR_ERR(cred);
goto err_put_ctx;
Expand Down Expand Up @@ -758,13 +759,13 @@ gss_destroy_cred(struct rpc_cred *rc)
* Lookup RPCSEC_GSS cred for the current process
*/
static struct rpc_cred *
gss_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int taskflags)
gss_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
return rpcauth_lookup_credcache(auth, acred, taskflags);
return rpcauth_lookup_credcache(auth, acred, flags);
}

static struct rpc_cred *
gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int taskflags)
gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
struct gss_auth *gss_auth = container_of(auth, struct gss_auth, rpc_auth);
struct gss_cred *cred = NULL;
Expand All @@ -785,13 +786,17 @@ gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int taskflags)
*/
cred->gc_flags = 0;
cred->gc_base.cr_ops = &gss_credops;
cred->gc_base.cr_flags = RPCAUTH_CRED_NEW;
cred->gc_service = gss_auth->service;
/* Is the caller prepared to initialise the credential? */
if (flags & RPCAUTH_LOOKUP_NEW)
goto out;
do {
err = gss_create_upcall(gss_auth, cred);
} while (err == -EAGAIN);
if (err < 0)
goto out_err;

out:
return &cred->gc_base;

out_err:
Expand All @@ -801,13 +806,21 @@ gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int taskflags)
}

static int
gss_match(struct auth_cred *acred, struct rpc_cred *rc, int taskflags)
gss_match(struct auth_cred *acred, struct rpc_cred *rc, int flags)
{
struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);

/*
* If the searchflags have set RPCAUTH_LOOKUP_NEW, then
* we don't really care if the credential has expired or not,
* since the caller should be prepared to reinitialise it.
*/
if ((flags & RPCAUTH_LOOKUP_NEW) && (rc->cr_flags & RPCAUTH_CRED_NEW))
goto out;
/* Don't match with creds that have expired. */
if (gss_cred->gc_ctx && time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
return 0;
out:
return (rc->cr_uid == acred->uid);
}

Expand Down
6 changes: 3 additions & 3 deletions net/sunrpc/auth_unix.c
View file
Expand Up @@ -75,7 +75,7 @@ unx_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)

atomic_set(&cred->uc_count, 1);
cred->uc_flags = RPCAUTH_CRED_UPTODATE;
if (flags & RPC_TASK_ROOTCREDS) {
if (flags & RPCAUTH_LOOKUP_ROOTCREDS) {
cred->uc_uid = 0;
cred->uc_gid = 0;
cred->uc_gids[0] = NOGROUP;
Expand Down Expand Up @@ -108,12 +108,12 @@ unx_destroy_cred(struct rpc_cred *cred)
* request root creds (e.g. for NFS swapping).
*/
static int
unx_match(struct auth_cred *acred, struct rpc_cred *rcred, int taskflags)
unx_match(struct auth_cred *acred, struct rpc_cred *rcred, int flags)
{
struct unx_cred *cred = (struct unx_cred *) rcred;
int i;

if (!(taskflags & RPC_TASK_ROOTCREDS)) {
if (!(flags & RPCAUTH_LOOKUP_ROOTCREDS)) {
int groups;

if (cred->uc_uid != acred->uid
Expand Down

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