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fs, nfs: convert nfs_client.cl_count from atomic_t to refcount_t

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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@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Elena Reshetova 2017-10-20 12:53:38 +03:00 • committed by Anna Schumaker
parent 2f62b5aa48
commit 212bf41d88
7 changed files with 33 additions and 32 deletions
Download patch file Download diff file Expand all files Collapse all files

12
fs/nfs/nfs4proc.c
View file

@ -4870,7 +4870,7 @@ 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);
@ -4918,7 +4918,7 @@ 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) {
@ -7499,7 +7499,7 @@ 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;
@ -8099,7 +8099,7 @@ 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);
@ -8128,7 +8128,7 @@ 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) {
@ -8179,7 +8179,7 @@ static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp,
struct rpc_task *ret;
ret = ERR_PTR(-EIO);
if (!atomic_inc_not_zero(&clp->cl_count))
if (!refcount_inc_not_zero(&clp->cl_count))
goto out_err;
ret = ERR_PTR(-ENOMEM);