linux-kernel - [PATCH 4.9 090/177] afs: Fix abort on signal while waiting for call completion

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Message-Id: <20171218152914.616253870@linuxfoundation.org>
Date:   Mon, 18 Dec 2017 16:48:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Dionne <marc.c.dionne@...istor.com>,
        David Howells <dhowells@...hat.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 090/177] afs: Fix abort on signal while waiting for call completion

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells@...hat.com>


[ Upstream commit 954cd6dc02a65065aecb7150962c0870c5b0e322 ]

Fix the way in which a call that's in progress and being waited for is
aborted in the case that EINTR is detected.  We should be sending
RX_USER_ABORT rather than RX_CALL_DEAD as the abort code.

Note that since the only two ways out of the loop are if the call completes
or if a signal happens, the kill-the-call clause after the loop has
finished can only happen in the case of EINTR.  This means that we only
have one abort case to deal with, not two, and the "KWC" case can never
happen and so can be deleted.

Note further that simply aborting the call isn't necessarily the best thing
here since at this point: the request has been entirely sent and it's
likely the server will do the operation anyway - whether we abort it or
not.  In future, we should punt the handling of the remainder of the call
off to a background thread.

Reported-by: Marc Dionne <marc.c.dionne@...istor.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/afs/rxrpc.c |   19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -492,7 +492,6 @@ call_complete:
  */
 static int afs_wait_for_call_to_complete(struct afs_call *call)
 {
-	const char *abort_why;
 	int ret;
 
 	DECLARE_WAITQUEUE(myself, current);
@@ -511,13 +510,8 @@ static int afs_wait_for_call_to_complete
 			continue;
 		}
 
-		abort_why = "KWC";
-		ret = call->error;
-		if (call->state == AFS_CALL_COMPLETE)
-			break;
-		abort_why = "KWI";
-		ret = -EINTR;
-		if (signal_pending(current))
+		if (call->state == AFS_CALL_COMPLETE ||
+		    signal_pending(current))
 			break;
 		schedule();
 	}
@@ -525,15 +519,14 @@ static int afs_wait_for_call_to_complete
 	remove_wait_queue(&call->waitq, &myself);
 	__set_current_state(TASK_RUNNING);
 
-	/* kill the call */
+	/* Kill off the call if it's still live. */
 	if (call->state < AFS_CALL_COMPLETE) {
-		_debug("call incomplete");
+		_debug("call interrupted");
 		rxrpc_kernel_abort_call(afs_socket, call->rxcall,
-					RX_CALL_DEAD, -ret, abort_why);
-	} else if (call->error < 0) {
-		ret = call->error;
+					RX_USER_ABORT, -EINTR, "KWI");
 	}
 
+	ret = call->error;
 	_debug("call complete");
 	afs_end_call(call);
 	_leave(" = %d", ret);