linux-kernel - Re: [PATCH] xhci: solve a double free problem while doing s4

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Date:   Thu, 10 Jun 2021 16:01:52 +0200
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     "Zhangjiantao (Kirin, nanjing)" <water.zhangjiantao@...wei.com>,
        "Xuetao (kirin)" <xuetao09@...wei.com>,
        "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "chenyu (U)" <chenyu56@...wei.com>,
        Caiyadong <caiyadong@...wei.com>,
        xuhaiyang <xuhaiyang5@...ilicon.com>
Subject: Re: [PATCH] xhci: solve a double free problem while doing s4

On Thu, Jun 10, 2021 at 04:45:54PM +0300, Mathias Nyman wrote:
> On 9.6.2021 17.22, Zhangjiantao (Kirin, nanjing) wrote:
> > when system is doing s4, the process of xhci_resume may be as below:
> > 1、xhci_mem_cleanup
> > 2、xhci_init->xhci_mem_init->xhci_mem_cleanup(when memory is not enough).
> > xhci_mem_cleanup will be executed twice when system is out of memory.
> > xhci->port_caps is freed in xhci_mem_cleanup,but it isn't set to NULL.
> > It will be freed twice when xhci_mem_cleanup is called the second time.
> > 
> 
> Thanks, nice catch
> 
> > We got following bug when system resumes from s4:
> > 
> > kernel BUG at mm/slub.c:309!
> > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> > CPU: 0 PID: 5929 Tainted: G S   W   5.4.96-arm64-desktop #1
> > pc : __slab_free+0x5c/0x424
> > lr : kfree+0x30c/0x32c
> > 
> > Call trace:
> >  __slab_free+0x5c/0x424
> >  kfree+0x30c/0x32c
> >  xhci_mem_cleanup+0x394/0x3cc
> >  xhci_mem_init+0x9ac/0x1070
> >  xhci_init+0x8c/0x1d0
> >  xhci_resume+0x1cc/0x5fc
> >  xhci_plat_resume+0x64/0x70
> >  platform_pm_thaw+0x28/0x60
> >  dpm_run_callback+0x54/0x24c
> >  device_resume+0xd0/0x200
> >  async_resume+0x24/0x60
> >  async_run_entry_fn+0x44/0x110
> >  process_one_work+0x1f0/0x490
> >  worker_thread+0x5c/0x450
> >  kthread+0x158/0x160
> >  ret_from_fork+0x10/0x24
> > 
> > Signed-off-by: Tao Xue <xuetao09@...wei.com>
> 
> Checkpatch complains:
> ERROR: Missing Signed-off-by: line by nominal patch author 'Zhangjiantao (Kirin, nanjing) <water.zhangjiantao@...wei.com>'
> 
> Is Zhangjiantao (Kirin, nanjing)  the correct author? If yes can I add 
> "Signed-off-by: Zhangjiantao (Kirin, nanjing) <water.zhangjiantao@...wei.com>?

Please note that it is generally a bad thing for others to add someone
else's s-o-b line, as it is a legal agreement.  It is best for them to
send it instead.

thanks,

greg k-h