Re: [PATCH] usb: gadget: f_ncm: Fix Kernel Panic due to access of invalid gadget ptr

[Hardik Gajjar <hgajjar@de.adit-jv.com>]

On Thu, Mar 07, 2024 at 04:45:13PM +0000, Greg KH wrote:
> On Thu, Mar 07, 2024 at 05:18:49PM +0100, Hardik Gajjar wrote:
> > In the scenario where the system enters suspend to RAM mode (STR) triggers
> > the disconnection of Dual Role USB Hub, and the UDC platform driver calls
> > usb_del_gadget_udc() to cleanup and delete the associated gadget.
> > 
> > However, at this point, the usb0 interface is not yet deleted, leading to
> > a race condition with the TCP/IP stack attempting to access the network
> > device parent (gadget pointer), through operations like the GETLINK net
> > message.
> > 
> > This patch addresses the issue by clearing the netdevice's parent device
> > pointer when the ncm unbinds, effectively preventing the race condition
> > during this critical phase.
> > 
> > Followinfg is the backtrace of such race condition
> > [ 3566.105792] Call trace:
> > [ 3566.105984] if_nlmsg_size+0x48/0x3b0
> > [ 3566.107497] rtnetlink_rcv_msg+0x1cc/0x408
> > [ 3566.107905] netlink_rcv_skb+0x12c/0x164
> > [ 3566.108264] rtnetlink_rcv+0x18/0x24
> > [ 3566.108851] netlink_unicast_kernel+0xc4/0x14c
> > [ 3566.109192] netlink_unicast+0x210/0x2b0
> > [ 3566.109606] netlink_sendmsg+0x2ec/0x360
> > [ 3566.110046] __sys_sendto+0x1b8/0x25c
> > [ 3566.111594] __arm64_sys_sendto+0x28/0x38
> > [ 3566.112599] el0_svc_common+0xb4/0x19c
> > [ 3566.112978] el0_svc_handler+0x74/0x98
> > [ 3566.113269] el0_svc+0x8/0xc
> > 
> > - code: if_nlmsg_size call the following function
> > 
> > static inline int rtnl_vfinfo_size(const struct net_device *dev,
> > 				   u32 ext_filter_mask)
> > {
> > 	// dev->dev.parent is not NULL
> > 	if (dev->dev.parent && (ext_filter_mask & RTEXT_FILTER_VF)) {
> > 		// dev_num_vf use the dev->dev.parent->bus lead to kernel panic.
> > 		int num_vfs = dev_num_vf(dev->dev.parent);
> > 		size_t size = nla_total_size(0);
> > 		size += num_vfs *
> > 			(nla_total_size(0) +
> > 			 nla_total_size(sizeof(struct ifla_vf_mac)) +
> > 			 nla_total_size(sizeof(struct ifla_vf_vlan)) +
> > 			 nla_total_size(0) + /* nest IFLA_VF_VLAN_LIST *
> > 
> > Signed-off-by: Hardik Gajjar <hgajjar@de.adit-jv.com>
> > ---
> >  drivers/usb/gadget/function/f_ncm.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> 
> What commit id does this fix?
> 
> thanks,
> 
> greg k-h

Hi Greg,

The network device parent is not being properly cleaned up during unbind since the initial commit of the driver.
In that case, should I mention the First commit ID of the driver as broken commit or
would you advice to say, For example "Clean up netdev parent in unbind".

Thanks,
Hardik