linux-kernel - Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem

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Message-ID: <11d7b29d-a45f-48e9-bff5-cb94150d0bdf@intel.com>
Date: Mon, 3 Nov 2025 13:02:06 +0200
From: Mathias Nyman <mathias.nyman@...el.com>
To: Michal Pecio <michal.pecio@...il.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Guangshuo Li <lgs201920130244@...il.com>,
 Wesley Cheng <quic_wcheng@...cinc.com>, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating
 interrupter array in xhci_mem_init()

On 11/3/25 10:40, Michal Pecio wrote:
> On Thu, 18 Sep 2025 21:08:38 +0800, Guangshuo Li wrote:
>> kcalloc_node() may fail. When the interrupter array allocation returns
>> NULL, subsequent code uses xhci->interrupters (e.g. in xhci_add_interrupter()
>> and in cleanup paths), leading to a potential NULL pointer dereference.
>>
>> Check the allocation and bail out to the existing fail path to avoid
>> the NULL dereference.
>>
>> Fixes: c99b38c412343 ("xhci: add support to allocate several interrupters")
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Guangshuo Li <lgs201920130244@...il.com>
>> ---
>>   drivers/usb/host/xhci-mem.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
>> index d698095fc88d..da257856e864 100644
>> --- a/drivers/usb/host/xhci-mem.c
>> +++ b/drivers/usb/host/xhci-mem.c
>> @@ -2505,7 +2505,8 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
>>   		       "Allocating primary event ring");
>>   	xhci->interrupters = kcalloc_node(xhci->max_interrupters, sizeof(*xhci->interrupters),
>>   					  flags, dev_to_node(dev));
>> -
>> +	if (!xhci->interrupters)
>> +		goto fail;
>>   	ir = xhci_alloc_interrupter(xhci, 0, flags);
>>   	if (!ir)
>>   		goto fail;
>> -- 
>> 2.43.0
> 
> Hi Greg and Mathias,
> 
> I noticed that this bug still exists in current 6.6 and 6.12 releases,
> what would be the sensible course of action to fix it?
> 

Not sure this qualifies for stable.
Is this something that has really happened in real life?

The stable-kernel-rules.rst states it should "fix a real bug that bothers people"

If kcalloc_node() fails to allocate that array of pointers then something
else is already badly messed up.

That being said, I don't object this being added to stable either

Thanks
Mathias