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

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Message-ID: <2025110342-rimless-change-0a95@gregkh>
Date: Mon, 3 Nov 2025 20:49:30 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Michal Pecio <michal.pecio@...il.com>
Cc: Mathias Nyman <mathias.nyman@...el.com>,
	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 Mon, Nov 03, 2025 at 09:40:36AM +0100, 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?
> 
> The patch from Guangshuo Li is a specific fix and it applies cleanly on
> those branches. By simulating allocation failure, I confirmed the bug
> and the fix on 6.6.113, which is identical to the current 6.6.116.
> 
> Mainline added an identical check in 83d98dea48eb ("usb: xhci: add
> individual allocation checks in xhci_mem_init()") which is a cleanup
> that has a merge conflict at least with 6.6.
> 
> The conflict seems superficial and probably the cleanup would have no
> side effects on 6.6/6.12, but I haven't really reviewed this and maybe
> it would be simpler to just take the targeted fix?

A backport is always appreciated if you want a patch in stable kernels.
And as this really can never be triggerd by a user, it's a low priority :)

thanks,

greg k-h