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sunrpc: fix RCU handling of gc_ctx field 

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@arndb.de>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Jeff Layton 2014-07-16 06:52:19 -04:00 committed by Trond Myklebust
parent a3b255717f
commit c5e6aecd03
1 changed files with 35 additions and 17 deletions
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52
net/sunrpc/auth_gss/auth_gss.c
View File

@ -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: