[PATCH v3] 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 before being implicitly
cast to *unsigned long*. 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, calling check_mul_overflow() and falling back
to 1 hour on an actual overflow...

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

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

Changes in version #3:
- changed the lease period overflow fallback to 1 hour, updated the patch
  description accordingly.

Changes in version #2:
- made use of check_mul_overflow() instead of mul_u32_u32();
- capped the multiplication result at ULONG_MAX instead of returning -ERANGE,
  keeping nfs4_set_lease_period() *void*;
- rewrote the patch description accordingly.

 fs/nfs/nfs4_fs.h    |    3 +--
 fs/nfs/nfs4proc.c   |    2 +-
 fs/nfs/nfs4renewd.c |   10 +++++++---
 fs/nfs/nfs4state.c  |    2 +-
 4 files changed, 10 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 void 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
@@ -5478,7 +5478,7 @@ 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);
+			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
@@ -137,11 +137,15 @@ 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)
+void nfs4_set_lease_period(struct nfs_client *clp, u32 period)
 {
+	unsigned long lease;
+
+	if (check_mul_overflow(period, HZ, &lease))
+		lease = 60UL * 60UL * HZ; /* one hour */
+
 	spin_lock(&clp->cl_lock);
 	clp->cl_lease_time = lease;
 	spin_unlock(&clp->cl_lock);
Index: linux-nfs/fs/nfs/nfs4state.c
===================================================================
--- linux-nfs.orig/fs/nfs/nfs4state.c
+++ linux-nfs/fs/nfs/nfs4state.c
@@ -103,7 +103,7 @@ 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);
+		nfs4_set_lease_period(clp, fsinfo.lease_time);
 		nfs4_schedule_state_renewal(clp);
 	}