linux-kernel - [PATCH] xen-blkback: fix two memleaks

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Date:	Thu, 10 Dec 2015 09:16:48 +0800
From:	Bob Liu <bob.liu@...cle.com>
To:	xen-devel@...ts.xenproject.org
Cc:	konrad.wilk@...cle.com, roger.pau@...rix.com,
	linux-kernel@...r.kernel.org, Bob Liu <bob.liu@...cle.com>
Subject: [PATCH] xen-blkback: fix two memleaks

This patch fixs two memleaks in konrad/xen.git/for-jens-4.5.
  backtrace:
    [<ffffffff817ba5e8>] kmemleak_alloc+0x28/0x50
    [<ffffffff81205e3b>] kmem_cache_alloc+0xbb/0x1d0
    [<ffffffff81534028>] xen_blkbk_probe+0x58/0x230
    [<ffffffff8146adb6>] xenbus_dev_probe+0x76/0x130
    [<ffffffff81511716>] driver_probe_device+0x166/0x2c0
    [<ffffffff815119bc>] __device_attach_driver+0xac/0xb0
    [<ffffffff8150fa57>] bus_for_each_drv+0x67/0x90
    [<ffffffff81511ab7>] __device_attach+0xc7/0x120
    [<ffffffff81511b23>] device_initial_probe+0x13/0x20
    [<ffffffff8151059a>] bus_probe_device+0x9a/0xb0
    [<ffffffff8150f0a1>] device_add+0x3b1/0x5c0
    [<ffffffff8150f47e>] device_register+0x1e/0x30
    [<ffffffff8146a9e8>] xenbus_probe_node+0x158/0x170
    [<ffffffff8146abaf>] xenbus_dev_changed+0x1af/0x1c0
    [<ffffffff8146b1bb>] backend_changed+0x1b/0x20
    [<ffffffff81468ca6>] xenwatch_thread+0xb6/0x160
unreferenced object 0xffff880007ba8ef8 (size 224):

  backtrace:
    [<ffffffff817ba5e8>] kmemleak_alloc+0x28/0x50
    [<ffffffff81205c73>] __kmalloc+0xd3/0x1e0
    [<ffffffff81534d87>] frontend_changed+0x2c7/0x580
    [<ffffffff8146af12>] xenbus_otherend_changed+0xa2/0xb0
    [<ffffffff8146b2c0>] frontend_changed+0x10/0x20
    [<ffffffff81468ca6>] xenwatch_thread+0xb6/0x160
    [<ffffffff810d3e97>] kthread+0xd7/0xf0
    [<ffffffff817c4a9f>] ret_from_fork+0x3f/0x70
    [<ffffffffffffffff>] 0xffffffffffffffff
unreferenced object 0xffff8800048dcd38 (size 224):

The first leak is caused by not put the be->blkif reference got in
xen_blkif_alloc(), while the second is not free blkif->rings in the right
place.

Signed-off-by: Bob Liu <bob.liu@...cle.com>
---
 drivers/block/xen-blkback/xenbus.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 44396b8..dabdb18 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -246,6 +246,9 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 	struct pending_req *req, *n;
 	unsigned int j, r;
 
+	if (!blkif->rings)
+		goto out;
+
 	for (r = 0; r < blkif->nr_rings; r++) {
 		struct xen_blkif_ring *ring = &blkif->rings[r];
 		unsigned int i = 0;
@@ -299,7 +302,14 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 		WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
 	}
 	blkif->nr_ring_pages = 0;
+	/*
+	 * blkif->rings was allocated in connect_ring, so we should free it in
+	 * disconnect.
+	 */
+	kfree(blkif->rings);
+	blkif->rings = NULL;
 
+out:
 	return 0;
 }
 
@@ -310,7 +320,6 @@ static void xen_blkif_free(struct xen_blkif *blkif)
 	xen_vbd_free(&blkif->vbd);
 
 	/* Make sure everything is drained before shutting down */
-	kfree(blkif->rings);
 	kmem_cache_free(xen_blkif_cachep, blkif);
 }
 
@@ -505,6 +514,8 @@ static int xen_blkbk_remove(struct xenbus_device *dev)
 			xen_blkif_put(be->blkif);
 	}
 
+	/* Put the reference got in xen_blkif_alloc(). */
+	xen_blkif_put(be->blkif);
 	kfree(be->mode);
 	kfree(be);
 	return 0;
-- 
1.7.10.4

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