linux-kernel - [PATCH] gadgetfs: Initialize CHIP to NULL before UDC probe

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Message-Id: <1393274155-2831-1-git-send-email-lkundrak@v3.sk>
Date:	Mon, 24 Feb 2014 21:35:55 +0100
From:	Lubomir Rintel <lkundrak@...sk>
To:	Felipe Balbi <balbi@...com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lubomir Rintel <lkundrak@...sk>
Subject: [PATCH] gadgetfs: Initialize CHIP to NULL before UDC probe

Otherwise the value from the last probe would be retained that possibly is
freed since (the UDC is removed) and therefore no longer relevant. Reproducible
with the dummy UDC:

  modprobe dummy_hcd
  mount -t gadgetfs gadgetfs /dev/gadget
  umount /dev/gadget
  rmmod dummy_hcd
  mount -t gadgetfs gadgetfs /dev/gadget

BUG: unable to handle kernel paging request at ffffffffa066fd9d
Call Trace:
 [<ffffffff811d0cd2>] ? d_alloc_name+0x22/0x50
 [<ffffffff812b74dc>] ? selinux_d_instantiate+0x1c/0x20
 [<ffffffffa067d687>] gadgetfs_create_file+0x27/0xa0 [gadgetfs]
 [<ffffffffa067da70>] ? setup_req.isra.4+0x80/0x80 [gadgetfs]
 [<ffffffffa067dbac>] gadgetfs_fill_super+0x13c/0x180 [gadgetfs]
 [<ffffffff811bc832>] mount_single+0x92/0xc0
 [<ffffffffa067d0f8>] gadgetfs_mount+0x18/0x20 [gadgetfs]
 [<ffffffff811bc8f9>] mount_fs+0x39/0x1b0
 [<ffffffff8116b220>] ? __alloc_percpu+0x10/0x20
 [<ffffffff811d6da3>] vfs_kern_mount+0x63/0xf0
 [<ffffffff811d93be>] do_mount+0x23e/0xac0
 [<ffffffff811660eb>] ? strndup_user+0x4b/0xf0
 [<ffffffff811d9f63>] SyS_mount+0x83/0xc0
 [<ffffffff81695b69>] system_call_fastpath+0x16/0x1b

Signed-off-by: Lubomir Rintel <lkundrak@...sk>
---
 drivers/usb/gadget/inode.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index b94c049..ee15628 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -2046,6 +2046,7 @@ gadgetfs_fill_super (struct super_block *sb, void *opts, int silent)
 		return -ESRCH;

 	/* fake probe to determine $CHIP */
+	CHIP = NULL;
 	usb_gadget_probe_driver(&probe_driver);
 	if (!CHIP)
 		return -ENODEV;
-- 
1.8.5.3

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