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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, David Howells <dhowells@redhat.com>
Subject: [PATCH 5.5 38/46] rxrpc: Fix sendmsg(MSG_WAITALL) handling
Date:   Tue,  7 Apr 2020 12:22:09 +0200
Message-Id: <20200407101503.512089696@linuxfoundation.org>
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From: David Howells <dhowells@redhat.com>

commit 498b577660f08cef5d9e78e0ed6dcd4c0939e98c upstream.

Fix the handling of sendmsg() with MSG_WAITALL for userspace to round the
timeout for when a signal occurs up to at least two jiffies as a 1 jiffy
timeout may end up being effectively 0 if jiffies wraps at the wrong time.

Fixes: bc5e3a546d55 ("rxrpc: Use MSG_WAITALL to tell sendmsg() to temporarily ignore signals")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/rxrpc/sendmsg.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -58,8 +58,8 @@ static int rxrpc_wait_for_tx_window_wait
 
 	rtt = READ_ONCE(call->peer->rtt);
 	rtt2 = nsecs_to_jiffies64(rtt) * 2;
-	if (rtt2 < 1)
-		rtt2 = 1;
+	if (rtt2 < 2)
+		rtt2 = 2;
 
 	timeout = rtt2;
 	tx_start = READ_ONCE(call->tx_hard_ack);