[PATCH 11/11] fs, nfs: convert nfs_client.cl_count from atomic_t to refcount_t

From: Elena Reshetova
Date: Fri Oct 20 2017 - 05:56:15 EST

atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable nfs_client.cl_count is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
---
fs/nfs/client.c | 10 +++++-----
fs/nfs/filelayout/filelayout.c | 12 ++++++------
fs/nfs/flexfilelayout/flexfilelayout.c | 12 ++++++------
fs/nfs/nfs4client.c | 10 +++++-----
fs/nfs/nfs4proc.c | 12 ++++++------
fs/nfs/nfs4state.c | 6 +++---
include/linux/nfs_fs_sb.h | 3 ++-
7 files changed, 33 insertions(+), 32 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 22880ef..0ac2fb1 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -163,7 +163,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)

clp->rpc_ops = clp->cl_nfs_mod->rpc_ops;

- atomic_set(&clp->cl_count, 1);
+ refcount_set(&clp->cl_count, 1);
clp->cl_cons_state = NFS_CS_INITING;

memcpy(&clp->cl_addr, cl_init->addr, cl_init->addrlen);
@@ -269,7 +269,7 @@ void nfs_put_client(struct nfs_client *clp)

nn = net_generic(clp->cl_net, nfs_net_id);

- if (atomic_dec_and_lock(&clp->cl_count, &nn->nfs_client_lock)) {
+ if (refcount_dec_and_lock(&clp->cl_count, &nn->nfs_client_lock)) {
list_del(&clp->cl_share_link);
nfs_cb_idr_remove_locked(clp);
spin_unlock(&nn->nfs_client_lock);
@@ -314,7 +314,7 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat
sap))
continue;

- atomic_inc(&clp->cl_count);
+ refcount_inc(&clp->cl_count);
return clp;
}
return NULL;
@@ -1006,7 +1006,7 @@ struct nfs_server *nfs_clone_server(struct nfs_server *source,
/* Copy data from the source */
server->nfs_client = source->nfs_client;
server->destroy = source->destroy;
- atomic_inc(&server->nfs_client->cl_count);
+ refcount_inc(&server->nfs_client->cl_count);
nfs_server_copy_userdata(server, source);

server->fsid = fattr->fsid;
@@ -1166,7 +1166,7 @@ static int nfs_server_list_show(struct seq_file *m, void *v)
clp->rpc_ops->version,
rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_ADDR),
rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_PORT),
- atomic_read(&clp->cl_count),
+ refcount_read(&clp->cl_count),
clp->cl_hostname);
rcu_read_unlock();

diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c
index 508126e..4e54d8b 100644
--- a/fs/nfs/filelayout/filelayout.c
+++ b/fs/nfs/filelayout/filelayout.c
@@ -471,10 +471,10 @@ filelayout_read_pagelist(struct nfs_pgio_header *hdr)
return PNFS_NOT_ATTEMPTED;

dprintk("%s USE DS: %s cl_count %d\n", __func__,
- ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));
+ ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count));

/* No multipath support. Use first DS */
- atomic_inc(&ds->ds_clp->cl_count);
+ refcount_inc(&ds->ds_clp->cl_count);
hdr->ds_clp = ds->ds_clp;
hdr->ds_commit_idx = idx;
fh = nfs4_fl_select_ds_fh(lseg, j);
@@ -515,10 +515,10 @@ filelayout_write_pagelist(struct nfs_pgio_header *hdr, int sync)

dprintk("%s ino %lu sync %d req %zu@%llu DS: %s cl_count %d\n",
__func__, hdr->inode->i_ino, sync, (size_t) hdr->args.count,
- offset, ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));
+ offset, ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count));

hdr->pgio_done_cb = filelayout_write_done_cb;
- atomic_inc(&ds->ds_clp->cl_count);
+ refcount_inc(&ds->ds_clp->cl_count);
hdr->ds_clp = ds->ds_clp;
hdr->ds_commit_idx = idx;
fh = nfs4_fl_select_ds_fh(lseg, j);
@@ -1064,9 +1064,9 @@ static int filelayout_initiate_commit(struct nfs_commit_data *data, int how)
goto out_err;

dprintk("%s ino %lu, how %d cl_count %d\n", __func__,
- data->inode->i_ino, how, atomic_read(&ds->ds_clp->cl_count));
+ data->inode->i_ino, how, refcount_read(&ds->ds_clp->cl_count));
data->commit_done_cb = filelayout_commit_done_cb;
- atomic_inc(&ds->ds_clp->cl_count);
+ refcount_inc(&ds->ds_clp->cl_count);
data->ds_clp = ds->ds_clp;
fh = select_ds_fh_from_commit(lseg, data->ds_commit_index);
if (fh)
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index ff55a0a..c75ad98 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -1726,10 +1726,10 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
vers = nfs4_ff_layout_ds_version(lseg, idx);

dprintk("%s USE DS: %s cl_count %d vers %d\n", __func__,
- ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count), vers);
+ ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count), vers);

hdr->pgio_done_cb = ff_layout_read_done_cb;
- atomic_inc(&ds->ds_clp->cl_count);
+ refcount_inc(&ds->ds_clp->cl_count);
hdr->ds_clp = ds->ds_clp;
fh = nfs4_ff_layout_select_ds_fh(lseg, idx);
if (fh)
@@ -1785,11 +1785,11 @@ ff_layout_write_pagelist(struct nfs_pgio_header *hdr, int sync)

dprintk("%s ino %lu sync %d req %zu@%llu DS: %s cl_count %d vers %d\n",
__func__, hdr->inode->i_ino, sync, (size_t) hdr->args.count,
- offset, ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count),
+ offset, ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count),
vers);

hdr->pgio_done_cb = ff_layout_write_done_cb;
- atomic_inc(&ds->ds_clp->cl_count);
+ refcount_inc(&ds->ds_clp->cl_count);
hdr->ds_clp = ds->ds_clp;
hdr->ds_commit_idx = idx;
fh = nfs4_ff_layout_select_ds_fh(lseg, idx);
@@ -1863,11 +1863,11 @@ static int ff_layout_initiate_commit(struct nfs_commit_data *data, int how)
vers = nfs4_ff_layout_ds_version(lseg, idx);

dprintk("%s ino %lu, how %d cl_count %d vers %d\n", __func__,
- data->inode->i_ino, how, atomic_read(&ds->ds_clp->cl_count),
+ data->inode->i_ino, how, refcount_read(&ds->ds_clp->cl_count),
vers);
data->commit_done_cb = ff_layout_commit_done_cb;
data->cred = ds_cred;
- atomic_inc(&ds->ds_clp->cl_count);
+ refcount_inc(&ds->ds_clp->cl_count);
data->ds_clp = ds->ds_clp;
fh = select_ds_fh_from_commit(lseg, data->ds_commit_index);
if (fh)
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index e9bea90..31b5bc0 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -483,7 +483,7 @@ static int nfs4_match_client(struct nfs_client *pos, struct nfs_client *new,
* ID and serverowner fields. Wait for CREATE_SESSION
* to finish. */
if (pos->cl_cons_state > NFS_CS_READY) {
- atomic_inc(&pos->cl_count);
+ refcount_inc(&pos->cl_count);
spin_unlock(&nn->nfs_client_lock);

nfs_put_client(*prev);
@@ -559,7 +559,7 @@ int nfs40_walk_client_list(struct nfs_client *new,
* way that a SETCLIENTID_CONFIRM to pos can succeed is
* if new and pos point to the same server:
*/
- atomic_inc(&pos->cl_count);
+ refcount_inc(&pos->cl_count);
spin_unlock(&nn->nfs_client_lock);

nfs_put_client(prev);
@@ -715,7 +715,7 @@ int nfs41_walk_client_list(struct nfs_client *new,
continue;

found:
- atomic_inc(&pos->cl_count);
+ refcount_inc(&pos->cl_count);
*result = pos;
status = 0;
break;
@@ -749,7 +749,7 @@ nfs4_find_client_ident(struct net *net, int cb_ident)
spin_lock(&nn->nfs_client_lock);
clp = idr_find(&nn->cb_ident_idr, cb_ident);
if (clp)
- atomic_inc(&clp->cl_count);
+ refcount_inc(&clp->cl_count);
spin_unlock(&nn->nfs_client_lock);
return clp;
}
@@ -804,7 +804,7 @@ nfs4_find_client_sessionid(struct net *net, const struct sockaddr *addr,
sid->data, NFS4_MAX_SESSIONID_LEN) != 0)
continue;

- atomic_inc(&clp->cl_count);
+ refcount_inc(&clp->cl_count);
spin_unlock(&nn->nfs_client_lock);
return clp;
}
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 57c38ea..350dbc9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4843,7 +4843,7 @@ static void nfs4_renew_release(void *calldata)
struct nfs4_renewdata *data = calldata;
struct nfs_client *clp = data->client;

- if (atomic_read(&clp->cl_count) > 1)
+ if (refcount_read(&clp->cl_count) > 1)
nfs4_schedule_state_renewal(clp);
nfs_put_client(clp);
kfree(data);
@@ -4891,7 +4891,7 @@ static int nfs4_proc_async_renew(struct nfs_client *clp, struct rpc_cred *cred,

if (renew_flags == 0)
return 0;
- if (!atomic_inc_not_zero(&clp->cl_count))
+ if (!refcount_inc_not_zero(&clp->cl_count))
return -EIO;
data = kmalloc(sizeof(*data), GFP_NOFS);
if (data == NULL) {
@@ -7472,7 +7472,7 @@ nfs4_run_exchange_id(struct nfs_client *clp, struct rpc_cred *cred,
struct nfs41_exchange_id_data *calldata;
int status;

- if (!atomic_inc_not_zero(&clp->cl_count))
+ if (!refcount_inc_not_zero(&clp->cl_count))
return ERR_PTR(-EIO);

status = -ENOMEM;
@@ -8072,7 +8072,7 @@ static void nfs41_sequence_release(void *data)
struct nfs4_sequence_data *calldata = data;
struct nfs_client *clp = calldata->clp;

- if (atomic_read(&clp->cl_count) > 1)
+ if (refcount_read(&clp->cl_count) > 1)
nfs4_schedule_state_renewal(clp);
nfs_put_client(clp);
kfree(calldata);
@@ -8101,7 +8101,7 @@ static void nfs41_sequence_call_done(struct rpc_task *task, void *data)
trace_nfs4_sequence(clp, task->tk_status);
if (task->tk_status < 0) {
dprintk("%s ERROR %d\n", __func__, task->tk_status);
- if (atomic_read(&clp->cl_count) == 1)
+ if (refcount_read(&clp->cl_count) == 1)
goto out;

if (nfs41_sequence_handle_errors(task, clp) == -EAGAIN) {
@@ -8149,7 +8149,7 @@ static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp,
.flags = RPC_TASK_ASYNC | RPC_TASK_TIMEOUT,
};

- if (!atomic_inc_not_zero(&clp->cl_count))
+ if (!refcount_inc_not_zero(&clp->cl_count))
return ERR_PTR(-EIO);
calldata = kzalloc(sizeof(*calldata), GFP_NOFS);
if (calldata == NULL) {
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 1887134..3bd79b8 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1177,7 +1177,7 @@ void nfs4_schedule_state_manager(struct nfs_client *clp)
if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0)
return;
__module_get(THIS_MODULE);
- atomic_inc(&clp->cl_count);
+ refcount_inc(&clp->cl_count);

/* The rcu_read_lock() is not strictly necessary, as the state
* manager is the only thread that ever changes the rpc_xprt
@@ -1269,7 +1269,7 @@ int nfs4_wait_clnt_recover(struct nfs_client *clp)

might_sleep();

- atomic_inc(&clp->cl_count);
+ refcount_inc(&clp->cl_count);
res = wait_on_bit_action(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING,
nfs_wait_bit_killable, TASK_KILLABLE);
if (res)
@@ -2510,7 +2510,7 @@ static void nfs4_state_manager(struct nfs_client *clp)
break;
if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0)
break;
- } while (atomic_read(&clp->cl_count) > 1);
+ } while (refcount_read(&clp->cl_count) > 1);
return;
out_error:
if (strlen(section))
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 74c4466..efcfe9d 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -9,6 +9,7 @@
#include <linux/sunrpc/xprt.h>

#include <linux/atomic.h>
+#include <linux/refcount.h>

struct nfs4_session;
struct nfs_iostats;
@@ -24,7 +25,7 @@ struct nfs41_impl_id;
* The nfs_client identifies our client state to the server.
*/
struct nfs_client {
- atomic_t cl_count;
+ refcount_t cl_count;
atomic_t cl_mds_count;
int cl_cons_state; /* current construction state (-ve: init error) */
#define NFS_CS_READY 0 /* ready to be used */
--
2.7.4