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From:   Kurt Manucredo <fuzzybritches0@gmail.com>
To:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com,
        bfields@fieldses.org, chuck.lever@oracle.com, davem@davemloft.net,
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Cc:     Kurt Manucredo <fuzzybritches0@gmail.com>,
        linux-nfs@vger.kernel.org, netdev@vger.kernel.org,
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Subject: [PATCH] net: sunrpc: xprt.c: fix shift-out-of-bounds in xprt_calc_majortimeo
Date:   Mon, 19 Apr 2021 16:36:03 +0000
Message-Id: <20210419163603.7-1-fuzzybritches0@gmail.com>
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Fix shift-out-of-bounds in xprt_calc_majortimeo().

UBSAN: shift-out-of-bounds in net/sunrpc/xprt.c:658:14
shift exponent 536871232 is too large for 64-bit type 'long u

Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com
Signed-off-by: Kurt Manucredo <fuzzybritches0@gmail.com>
---
 net/sunrpc/xprt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 691ccf8049a4..07128ac3d51d 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -655,7 +655,10 @@ static unsigned long xprt_calc_majortimeo(struct rpc_rqst *req)
 	unsigned long majortimeo = req->rq_timeout;
 
 	if (to->to_exponential)
-		majortimeo <<= to->to_retries;
+		if (to->to_retries >= sizeof(majortimeo) * 8)
+			majortimeo = to->to_maxval;
+		else
+			majortimeo <<= to->to_retries;
 	else
 		majortimeo += to->to_increment * to->to_retries;
 	if (majortimeo > to->to_maxval || majortimeo == 0)
-- 
2.30.2