linux-kernel - [ 25/69] usb: musb_gadget: fix crash caused by dangling pointer

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Message-Id: <20120617175944.881744995@decadent.org.uk>
Date:	Sun, 17 Jun 2012 19:00:06 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Grazvydas Ignotas <notasas@...il.com>,
	Felipe Balbi <balbi@...com>
Subject: [ 25/69] usb: musb_gadget: fix crash caused by dangling pointer

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

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

From: Grazvydas Ignotas <notasas@...il.com>

commit 08f75bf14fadaa81fe362d5acda9b77b113dd0a2 upstream.

usb_ep_ops.disable must clear external copy of the endpoint descriptor,
otherwise musb crashes after loading/unloading several gadget modules
in a row:

Unable to handle kernel paging request at virtual address bf013730
pgd = c0004000
[bf013730] *pgd=8f26d811, *pte=00000000, *ppte=00000000
Internal error: Oops: 7 [#1]
Modules linked in: g_cdc [last unloaded: g_file_storage]
CPU: 0    Not tainted  (3.2.17 #647)
PC is at musb_gadget_enable+0x4c/0x24c
LR is at _raw_spin_lock_irqsave+0x4c/0x58
[<c027c030>] (musb_gadget_enable+0x4c/0x24c) from [<bf01b760>] (gether_connect+0x3c/0x19c [g_cdc])
[<bf01b760>] (gether_connect+0x3c/0x19c [g_cdc]) from [<bf01ba1c>] (ecm_set_alt+0x15c/0x180 [g_cdc])
[<bf01ba1c>] (ecm_set_alt+0x15c/0x180 [g_cdc]) from [<bf01ecd4>] (composite_setup+0x85c/0xac4 [g_cdc])
[<bf01ecd4>] (composite_setup+0x85c/0xac4 [g_cdc]) from [<c027b744>] (musb_g_ep0_irq+0x844/0x924)
[<c027b744>] (musb_g_ep0_irq+0x844/0x924) from [<c027a97c>] (musb_interrupt+0x79c/0x864)
[<c027a97c>] (musb_interrupt+0x79c/0x864) from [<c027aaa8>] (generic_interrupt+0x64/0x7c)
[<c027aaa8>] (generic_interrupt+0x64/0x7c) from [<c00797cc>] (handle_irq_event_percpu+0x28/0x178)
...

Signed-off-by: Grazvydas Ignotas <notasas@...il.com>
Signed-off-by: Felipe Balbi <balbi@...com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/musb/musb_gadget.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index f42c29b..95918da 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -1232,6 +1232,7 @@ static int musb_gadget_disable(struct usb_ep *ep)
 	}
 
 	musb_ep->desc = NULL;
+	musb_ep->end_point.desc = NULL;
 
 	/* abort all pending DMA and requests */
 	nuke(musb_ep, -ESHUTDOWN);


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