[PATCH] NFSv4: prevent integer overflow while calling nfs4_set_lease_period()

[Sergey Shtylyov <s.shtylyov@omp.ru>]

The nfs_client::cl_lease_time field (as well as the jiffies variable it's
used with) is declared as *unsigned long*, which is 32-bit type on 32-bit
arches and 64-bit type on 64-bit arches. When nfs4_set_lease_period() that
sets nfs_client::cl_lease_time is called, 32-bit nfs_fsinfo::lease_time
field is multiplied by HZ -- that might overflow *unsigned long* on 32-bit
arches.  Actually, there's no need to multiply by HZ at all the call sites
of nfs4_set_lease_period() -- it makes more sense to do that once, inside
that function (using mul_u32_u32(), as it produces a better code on 32-bit
x86 arch), also checking for an overflow there and returning -ERANGE if it
does happen (we're also making that function *int* instead of *void* and
adding the result checks to its callers)...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Cc: stable@vger.kernel.org

---
This patch is against the master branch of Trond Myklebust's linux-nfs.git repo.

 fs/nfs/nfs4_fs.h    |    3 +--
 fs/nfs/nfs4proc.c   |    3 ++-
 fs/nfs/nfs4renewd.c |   13 ++++++++++---
 fs/nfs/nfs4state.c  |    4 +++-
 4 files changed, 16 insertions(+), 7 deletions(-)

Index: linux-nfs/fs/nfs/nfs4_fs.h
===================================================================
--- linux-nfs.orig/fs/nfs/nfs4_fs.h
+++ linux-nfs/fs/nfs/nfs4_fs.h
@@ -464,8 +464,7 @@ struct nfs_client *nfs4_alloc_client(con
 extern void nfs4_schedule_state_renewal(struct nfs_client *);
 extern void nfs4_kill_renewd(struct nfs_client *);
 extern void nfs4_renew_state(struct work_struct *);
-extern void nfs4_set_lease_period(struct nfs_client *clp, unsigned long lease);
-
+extern int nfs4_set_lease_period(struct nfs_client *clp, u32 period);
 
 /* nfs4state.c */
 extern const nfs4_stateid current_stateid;
Index: linux-nfs/fs/nfs/nfs4proc.c
===================================================================
--- linux-nfs.orig/fs/nfs/nfs4proc.c
+++ linux-nfs/fs/nfs/nfs4proc.c
@@ -5403,7 +5403,8 @@ static int nfs4_do_fsinfo(struct nfs_ser
 		err = _nfs4_do_fsinfo(server, fhandle, fsinfo);
 		trace_nfs4_fsinfo(server, fhandle, fsinfo->fattr, err);
 		if (err == 0) {
-			nfs4_set_lease_period(server->nfs_client, fsinfo->lease_time * HZ);
+			err = nfs4_set_lease_period(server->nfs_client,
+						    fsinfo->lease_time);
 			break;
 		}
 		err = nfs4_handle_exception(server, err, &exception);
Index: linux-nfs/fs/nfs/nfs4renewd.c
===================================================================
--- linux-nfs.orig/fs/nfs/nfs4renewd.c
+++ linux-nfs/fs/nfs/nfs4renewd.c
@@ -137,15 +137,22 @@ nfs4_kill_renewd(struct nfs_client *clp)
  * nfs4_set_lease_period - Sets the lease period on a nfs_client
  *
  * @clp: pointer to nfs_client
- * @lease: new value for lease period
+ * @period: new value for lease period (in seconds)
  */
-void nfs4_set_lease_period(struct nfs_client *clp,
-		unsigned long lease)
+int nfs4_set_lease_period(struct nfs_client *clp, u32 period)
 {
+	u64 result = mul_u32_u32(period, HZ);
+	unsigned long lease = result;
+
+	/* First see if period * HZ actually fits into unsigned long... */
+	if (result > ULONG_MAX)
+		return -ERANGE;
+
 	spin_lock(&clp->cl_lock);
 	clp->cl_lease_time = lease;
 	spin_unlock(&clp->cl_lock);
 
 	/* Cap maximum reconnect timeout at 1/2 lease period */
 	rpc_set_connect_timeout(clp->cl_rpcclient, lease, lease >> 1);
+	return 0;
 }
Index: linux-nfs/fs/nfs/nfs4state.c
===================================================================
--- linux-nfs.orig/fs/nfs/nfs4state.c
+++ linux-nfs/fs/nfs/nfs4state.c
@@ -103,7 +103,9 @@ static int nfs4_setup_state_renewal(stru
 
 	status = nfs4_proc_get_lease_time(clp, &fsinfo);
 	if (status == 0) {
-		nfs4_set_lease_period(clp, fsinfo.lease_time * HZ);
+		status = nfs4_set_lease_period(clp, fsinfo.lease_time);
+		if (status)
+			return status;
 		nfs4_schedule_state_renewal(clp);
 	}