Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()

[Michal Pecio <michal.pecio@gmail.com>]

On Mon, 3 Nov 2025 13:02:06 +0200, Mathias Nyman wrote:
> > 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.

I don't know how the reported found it, but it can obviously happen when
the driver is bound to a new xHCI controller under OOM conditions.

So maybe not very often, but xHCI hotplug is a thing in Thunderbolt and
OOM happens sometimes too, so it's not exactly impossible either.

I thought it's usual to fix such bugs when they are known.
Simulated allocation failure before/after:

[ +30,414603] xhci_hcd 0000:00:10.0: xHCI Host Controller
[  +0,000012] xhci_hcd 0000:00:10.0: new USB bus registered, assigned bus number 2
[  +0,000159] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  +0,000004] #PF: supervisor read access in kernel mode
[  +0,000002] #PF: error_code(0x0000) - not-present page
[  +0,000002] PGD 0 P4D 0 
[  +0,000003] Oops: 0000 [#1] PREEMPT SMP
[  +0,000004] CPU: 1 PID: 4270 Comm: insmod Not tainted 6.6.113 #11
[  +0,000003] Hardware name: HP HP EliteDesk 705 G3 MT/8265, BIOS P06 Ver. 02.45 07/16/2024
[  +0,000003] RIP: 0010:xhci_add_interrupter+0x25/0x130 [xhci_hcd]

[  +0,042495] xhci_hcd 0000:00:10.0: xHCI Host Controller
[  +0,000012] xhci_hcd 0000:00:10.0: new USB bus registered, assigned bus number 2
[  +0,007193] xhci_hcd 0000:00:10.0: can't setup: -12
[  +0,000010] xhci_hcd 0000:00:10.0: USB bus 2 deregistered
[  +0,000080] xhci_hcd 0000:00:10.0: init 0000:00:10.0 fail, -12
[  +0,000004] xhci_hcd: probe of 0000:00:10.0 failed with error -12