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

[Mathias Nyman]

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@xxxxxxxxxxxxxxx
> > Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
> > ---
> >   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