sunrpc:fix shift-out-of-bounds for majortimeo

For UDP proto, to->to_exponential is true. Too large to_retries
may cause shift-out-of-bounds error for "majortime <<= to_retries"
Add sanity checks to fix it.

Signed-off-by: zhangjian <[email protected]>
---
 net/sunrpc/xprt.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 48a3618cbb29..c62f9998ffe9 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -656,10 +656,16 @@ static unsigned long xprt_calc_majortimeo(struct
rpc_rqst *req,
 {
 	unsigned long majortimeo = req->rq_timeout;

-	if (to->to_exponential)
-		majortimeo <<= to->to_retries;
-	else
+	if (to->to_exponential) {
+		if (to->to_retries >= BITS_PER_LONG ||
+		    majortimeo > (ULONG_MAX >> to->to_retries)) {
+			majortimeo = ULONG_MAX;
+		} else {
+			majortimeo <<= to->to_retries;
+		}
+	} else {
 		majortimeo += to->to_increment * to->to_retries;
+	}
 	if (majortimeo > to->to_maxval || majortimeo == 0)
 		majortimeo = to->to_maxval;
 	return majortimeo;
-- 
2.33.0