From: Ajay Kaher <ajay.kaher@samsung.com>
To: gregkh@linuxfoundation.org
Cc: stern@rowland.harvard.edu, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org, aman.deep@samsung.com,
hemanshu.s@samsung.com, ajay.kaher@samsung.com
Subject: [PATCH v4] USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously
Date: Tue, 28 Mar 2017 08:09:32 -0400 [thread overview]
Message-ID: <1490702972-22560-1-git-send-email-ajay.kaher@samsung.com> (raw)
In-Reply-To: CGME20170328121013epcas5p493f1509064350349fbcdb655793d8d4e@epcas5p4.samsung.com
Greg, sending patch again using git send-email, please apply.
Let me know if still any issue.
There is race condition when two USB class drivers try to call
init_usb_class at the same time and leads to crash.
code path: probe->usb_register_dev->init_usb_class
To solve this, mutex locking has been added in init_usb_class() and
destroy_usb_class().
As pointed by Alan, removed "if (usb_class)" test from destroy_usb_class()
because usb_class can never be NULL there.
Signed-off-by: Ajay Kaher <ajay.kaher@samsung.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
---
drivers/usb/core/file.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/core/file.c b/drivers/usb/core/file.c
index 822ced9..422ce7b 100644
--- a/drivers/usb/core/file.c
+++ b/drivers/usb/core/file.c
@@ -27,6 +27,7 @@
#define MAX_USB_MINORS 256
static const struct file_operations *usb_minors[MAX_USB_MINORS];
static DECLARE_RWSEM(minor_rwsem);
+static DEFINE_MUTEX(init_usb_class_mutex);
static int usb_open(struct inode *inode, struct file *file)
{
@@ -109,8 +110,9 @@ static void release_usb_class(struct kref *kref)
static void destroy_usb_class(void)
{
- if (usb_class)
- kref_put(&usb_class->kref, release_usb_class);
+ mutex_lock(&init_usb_class_mutex);
+ kref_put(&usb_class->kref, release_usb_class);
+ mutex_unlock(&init_usb_class_mutex);
}
int usb_major_init(void)
@@ -171,7 +173,10 @@ int usb_register_dev(struct usb_interface *intf,
if (intf->minor >= 0)
return -EADDRINUSE;
+ mutex_lock(&init_usb_class_mutex);
retval = init_usb_class();
+ mutex_unlock(&init_usb_class_mutex);
+
if (retval)
return retval;
--
2.7.4
next parent reply other threads:[~2017-03-28 12:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20170328121013epcas5p493f1509064350349fbcdb655793d8d4e@epcas5p4.samsung.com>
2017-03-28 12:09 ` Ajay Kaher [this message]
2017-03-29 9:56 ` [PATCH v4] USB: Proper handling of Race Condition when two USB class drivers try to call init_usb_class simultaneously Greg KH
2017-03-09 12:10 Subject: [PATCH v4] USB:Core: BugFix: " gregkh
2017-03-07 15:00 ` Alan Stern
2017-03-09 11:34 ` Ajay Kaher
[not found] ` <CGME20170307150103epcas2p348320fdfbb176978d084d8f2b7b9a049@epcms5p2>
2017-03-17 10:56 ` [PATCH v4] USB: " Ajay Kaher
2017-03-23 7:18 ` gregkh
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