linux-kernel - Possible memory leak in request

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Date:	Tue, 07 Jul 2009 16:17:00 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Greg Kroah-Hartman <gregkh@...e.de>,
	Ming Lei <tom.leiming@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Possible memory leak in request_firmware()

Hi,

I get a couple kmemleak reports like below which I think happen on the
failure path (-ENOENT) of a request_firmware() call:

unreferenced object 0xc355fdb0 (size 256):
  comm "NetworkManager", pid 2606, jiffies 4294902882
  backtrace:
    [<c01e0c3a>] create_object+0xfa/0x250
    [<c01e1e7d>] kmemleak_alloc+0x5d/0x70
    [<c01dac1b>] kmem_cache_alloc+0x14b/0x190
    [<c03a0c4c>] _request_firmware+0x11c/0x530
    [<c03a1102>] request_firmware+0x12/0x20
    [<f95f6591>] iwl_mac_start+0xa1/0x850 [iwlagn]
    [<f8fb08c1>] ieee80211_open+0x2e1/0x860 [mac80211]
    [<c048459a>] dev_open+0xba/0x100
    [<c0483ab9>] dev_change_flags+0x139/0x1d0
    [<c048d392>] do_setlink+0x282/0x410
    [<c048ea81>] rtnl_setlink+0xf1/0x130
    [<c048e285>] rtnetlink_rcv_msg+0x165/0x200
    [<c049fac6>] netlink_rcv_skb+0x76/0xa0
    [<c048e10e>] rtnetlink_rcv+0x1e/0x30
    [<c049f7fb>] netlink_unicast+0x23b/0x250
    [<c04a02db>] netlink_sendmsg+0x1db/0x2d0

The f_dev in _request_firmware() is allocated via the fw_setup_device()
and fw_register_device() calls and its class set to firmware_class (the
class release function is fw_dev_release).

Commit 6acf70f078ca replaced the kfree(dev) in fw_dev_release() with a
put_device() call but my understanding is that the release function is
called via put_device -> kobject_put -> kref_put -> koject_release etc.
and it should call kfree since it's the last to see this device
structure alive.

Because of that, the _request_firmware() function on its -ENOENT error
path only calls device_unregister(f_dev) which would eventually call
fw_dev_release() but there is no kfree (the subsequent put_device call
would just make the kref negative).

The patch below may fix the problem but it's only later tonight that I
can test it and confirm:

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index ddeb819..12e6e64 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -357,7 +357,7 @@ static void fw_dev_release(struct device *dev)
 	kfree(fw_priv->pages);
 	kfree(fw_priv->fw_id);
 	kfree(fw_priv);
-	put_device(dev);
+	kfree(dev);

 	module_put(THIS_MODULE);
 }
@@ -407,14 +407,13 @@ static int fw_register_device(struct device **dev_p, const char *fw_name,
 	retval = device_register(f_dev);
 	if (retval) {
 		dev_err(device, "%s: device_register failed\n", __func__);
+		kfree(fw_priv->fw_id);
 		put_device(f_dev);
-		goto error_kfree_fw_id;
+		return retval;
 	}
 	*dev_p = f_dev;
 	return 0;

-error_kfree_fw_id:
-	kfree(fw_priv->fw_id);
 error_kfree:
 	kfree(f_dev);
 	kfree(fw_priv);

-- 
Catalin

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