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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, Martin Brandenburg <martin@omnibond.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 4.9 03/66] orangefs: initialize op on loop restart in orangefs_devreq_read
Date:   Mon, 29 Jan 2018 13:56:27 +0100
Message-Id: <20180129123840.031212635@linuxfoundation.org>
In-Reply-To: <20180129123839.842860149@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Martin Brandenburg <martin@omnibond.com>

commit a0ec1ded22e6a6bc41981fae22406835b006a66e upstream.

In orangefs_devreq_read, there is a loop which picks an op off the list
of pending ops.  If the loop fails to find an op, there is nothing to
read, and it returns EAGAIN.  If the op has been given up on, the loop
is restarted via a goto.  The bug is that the variable which the found
op is written to is not reinitialized, so if there are no more eligible
ops on the list, the code runs again on the already handled op.

This is triggered by interrupting a process while the op is being copied
to the client-core.  It's a fairly small window, but it's there.

Signed-off-by: Martin Brandenburg <martin@omnibond.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/orangefs/devorangefs-req.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/orangefs/devorangefs-req.c
+++ b/fs/orangefs/devorangefs-req.c
@@ -161,7 +161,7 @@ static ssize_t orangefs_devreq_read(stru
 	struct orangefs_kernel_op_s *op, *temp;
 	__s32 proto_ver = ORANGEFS_KERNEL_PROTO_VERSION;
 	static __s32 magic = ORANGEFS_DEVREQ_MAGIC;
-	struct orangefs_kernel_op_s *cur_op = NULL;
+	struct orangefs_kernel_op_s *cur_op;
 	unsigned long ret;
 
 	/* We do not support blocking IO. */
@@ -181,6 +181,7 @@ static ssize_t orangefs_devreq_read(stru
 	}
 
 restart:
+	cur_op = NULL;
 	/* Get next op (if any) from top of list. */
 	spin_lock(&orangefs_request_list_lock);
 	list_for_each_entry_safe(op, temp, &orangefs_request_list, list) {