linux-kernel - Re: BUG kmalloc-16: Object already free

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Message-ID: <20080929181752.GA2027@debian>
Date:	Mon, 29 Sep 2008 23:47:52 +0530
From:	Rabin Vincent <rabin@....in>
To:	Justin Mattock <justinmattock@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	marcel@...tmann.org, linux-bluetooth@...r.kernel.org
Subject: Re: BUG kmalloc-16: Object already free

On Sun, Sep 28, 2008 at 03:54:23PM -0700, Justin Mattock wrote:
> After frying my system, I'm finally up and
> running. Not sure if this was due to a git-pull
> (only be a few days since the last pull), or what:
> when waking from suspend I see this
> (I know it says tainted in it, so this will be the only noise you'll
> here from me on this);
> 
> [  274.327003] =============================================================================
> [  274.327528] BUG kmalloc-16: Object already free
> [  274.327877] -----------------------------------------------------------------------------
> [  274.327879]
> [  274.327890] INFO: Allocated in btusb_open+0x82/0x16f [btusb] age=0
> cpu=1 pid=3763
> [  274.327899] INFO: Freed in btusb_open+0x13d/0x16f [btusb] age=0
> cpu=1 pid=3763
> [  274.327905] INFO: Slab 0xc139a100 objects=64 used=62 fp=0xdcd08100
> flags=0x400000c3

There's a commit in the latest git which looks like it will solve the
btusb suspend/resume issues: 5fbcd260.. ("[Bluetooth] Fix USB disconnect
handling of btusb driver").

Marcel / linux-bluetooth, I think this double free is a separate issue
with the error handling, and the following patch should fix it.

---
From: Rabin Vincent <rabin@....in>
Subject: [PATCH] btusb, bpa10x: fix double frees on error paths

Justin Mattock reported this double free in btusb:

  BUG kmalloc-16: Object already free
  -----------------------------------------------------------------------------

  INFO: Allocated in btusb_open+0x82/0x16f [btusb] age=3D0 cpu=3D1 pid=3D3763
  INFO: Freed in btusb_open+0x13d/0x16f [btusb] age=3D0 cpu=3D1 pid=3D3763

This occurs because the urb's transfer buffer is being freed separately
in the error path even though the URB_FREE_BUFFER transfer_flag is set
on the urb.

There are similar cases elsewhere in btusb and in bpa10x.  Fix all of
them by removing the additional kfree()'s.

Reported-by: Justin Mattock <justinmattock@...il.com>
Signed-off-by: Rabin Vincent <rabin@....in>
---
 drivers/bluetooth/bpa10x.c |    2 --
 drivers/bluetooth/btusb.c  |    3 ---
 2 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/bpa10x.c b/drivers/bluetooth/bpa10x.c
index 1e55a65..32f3a8e 100644
--- a/drivers/bluetooth/bpa10x.c
+++ b/drivers/bluetooth/bpa10x.c
@@ -256,7 +256,6 @@ static inline int bpa10x_submit_intr_urb(struct hci_dev *hdev)
 		BT_ERR("%s urb %p submission failed (%d)",
 						hdev->name, urb, -err);
 		usb_unanchor_urb(urb);
-		kfree(buf);
 	}
 
 	usb_free_urb(urb);
@@ -298,7 +297,6 @@ static inline int bpa10x_submit_bulk_urb(struct hci_dev *hdev)
 		BT_ERR("%s urb %p submission failed (%d)",
 						hdev->name, urb, -err);
 		usb_unanchor_urb(urb);
-		kfree(buf);
 	}
 
 	usb_free_urb(urb);
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 29ae998..262e9be 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -271,7 +271,6 @@ static int btusb_submit_intr_urb(struct hci_dev *hdev)
 		BT_ERR("%s urb %p submission failed (%d)",
 						hdev->name, urb, -err);
 		usb_unanchor_urb(urb);
-		kfree(buf);
 	}
 
 	usb_free_urb(urb);
@@ -354,7 +353,6 @@ static int btusb_submit_bulk_urb(struct hci_dev *hdev)
 		BT_ERR("%s urb %p submission failed (%d)",
 						hdev->name, urb, -err);
 		usb_unanchor_urb(urb);
-		kfree(buf);
 	}
 
 	usb_free_urb(urb);
@@ -475,7 +473,6 @@ static int btusb_submit_isoc_urb(struct hci_dev *hdev)
 		BT_ERR("%s urb %p submission failed (%d)",
 						hdev->name, urb, -err);
 		usb_unanchor_urb(urb);
-		kfree(buf);
 	}
 
 	usb_free_urb(urb);
-- 
1.5.6.5

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