The handling of the gc_ctx pointer only seems to be partially RCU-safe.
The assignment and freeing are done using RCU, but many places in the
code seem to dereference that pointer without proper RCU safeguards.
Fix them to use rcu_dereference and to rcu_read_lock/unlock, and to
properly handle the case where the pointer is NULL.
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
---
net/sunrpc/auth_gss/auth_gss.c | 52 ++++++++++++++++++++++++++++--------------
1 file changed, 35 insertions(+), 17 deletions(-)
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 73854314fb85..afb292cd797d 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -183,8 +183,9 @@ gss_cred_get_ctx(struct rpc_cred *cred)
struct gss_cl_ctx *ctx = NULL;
rcu_read_lock();
- if (gss_cred->gc_ctx)
- ctx = gss_get_ctx(gss_cred->gc_ctx);
+ ctx = rcu_dereference(gss_cred->gc_ctx);
+ if (ctx)
+ gss_get_ctx(ctx);
rcu_read_unlock();
return ctx;
}
@@ -1207,13 +1208,13 @@ gss_destroying_context(struct rpc_cred *cred)
{
struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
struct gss_auth *gss_auth = container_of(cred->cr_auth, struct gss_auth, rpc_auth);
+ struct gss_cl_ctx *ctx = rcu_dereference_protected(gss_cred->gc_ctx, 1);
struct rpc_task *task;
- if (gss_cred->gc_ctx == NULL ||
- test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
+ if (test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
return 0;
- gss_cred->gc_ctx->gc_proc = RPC_GSS_PROC_DESTROY;
+ ctx->gc_proc = RPC_GSS_PROC_DESTROY;
cred->cr_ops = &gss_nullops;
/* Take a reference to ensure the cred will be destroyed either
@@ -1274,7 +1275,7 @@ gss_destroy_nullcred(struct rpc_cred *cred)
{
struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
struct gss_auth *gss_auth = container_of(cred->cr_auth, struct gss_auth, rpc_auth);
- struct gss_cl_ctx *ctx = gss_cred->gc_ctx;
+ struct gss_cl_ctx *ctx = rcu_dereference_protected(gss_cred->gc_ctx, 1);
RCU_INIT_POINTER(gss_cred->gc_ctx, NULL);
call_rcu(&cred->cr_rcu, gss_free_cred_callback);
@@ -1349,20 +1350,30 @@ gss_cred_init(struct rpc_auth *auth, struct rpc_cred *cred)
static char *
gss_stringify_acceptor(struct rpc_cred *cred)
{
- char *string;
+ char *string = NULL;
struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
- struct xdr_netobj *acceptor = &gss_cred->gc_ctx->gc_acceptor;
+ struct gss_cl_ctx *ctx;
+ struct xdr_netobj *acceptor;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(gss_cred->gc_ctx);
+ if (!ctx)
+ goto out;
+
+ acceptor = &ctx->gc_acceptor;
/* no point if there's no string */
if (!acceptor->len)
- return NULL;
+ goto out;
string = kmalloc(acceptor->len + 1, GFP_KERNEL);
if (!string)
- return string;
+ goto out;
memcpy(string, acceptor->data, acceptor->len);
string[acceptor->len] = '\0';
+out:
+ rcu_read_unlock();
return string;
}
@@ -1374,15 +1385,16 @@ static int
gss_key_timeout(struct rpc_cred *rc)
{
struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);
+ struct gss_cl_ctx *ctx;
unsigned long now = jiffies;
unsigned long expire;
- if (gss_cred->gc_ctx == NULL)
- return -EACCES;
-
- expire = gss_cred->gc_ctx->gc_expiry - (gss_key_expire_timeo * HZ);
-
- if (time_after(now, expire))
+ rcu_read_lock();
+ ctx = rcu_dereference(gss_cred->gc_ctx);
+ if (ctx)
+ expire = ctx->gc_expiry - (gss_key_expire_timeo * HZ);
+ rcu_read_unlock();
+ if (!ctx || time_after(now, expire))
return -EACCES;
return 0;
}
@@ -1391,13 +1403,19 @@ static int
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);
+ struct gss_cl_ctx *ctx;
int ret;
if (test_bit(RPCAUTH_CRED_NEW, &rc->cr_flags))
goto out;
/* Don't match with creds that have expired. */
- if (time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
+ rcu_read_lock();
+ ctx = rcu_dereference(gss_cred->gc_ctx);
+ if (!ctx || time_after(jiffies, ctx->gc_expiry)) {
+ rcu_read_unlock();
return 0;
+ }
+ rcu_read_unlock();
if (!test_bit(RPCAUTH_CRED_UPTODATE, &rc->cr_flags))
return 0;
out:
--
1.9.3
--
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