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

Guangshuo Li posted 1 patch 4 months, 3 weeks ago 
drivers/usb/host/xhci-mem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
[PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()
Posted by Guangshuo Li 4 months, 3 weeks ago 
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@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.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
Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()
Posted by Michal Pecio 3 months, 1 week ago 
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@vger.kernel.org
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.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?

Regards,
Michal
Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()
Posted by Greg Kroah-Hartman 3 months, 1 week ago 
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@vger.kernel.org
> > Signed-off-by: Guangshuo Li <lgs201920130244@gmail.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
Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()
Posted by Mathias Nyman 3 months, 1 week ago 
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@vger.kernel.org
>> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.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
Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()
Posted by Michal Pecio 3 months, 1 week ago 
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
Re: [PATCH] usb: xhci: Check kcalloc_node() when allocating interrupter array in xhci_mem_init()
Posted by Michal Pecio 4 months, 3 weeks ago 
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@vger.kernel.org
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.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;

This is a patch against some old kernel, this exact check has been
added in v6.16 by 83d98dea48eb6.

But it's missing Fixes and Cc:stable, so 6.6 and 6.12 were left broken.

>  	ir = xhci_alloc_interrupter(xhci, 0, flags);
>  	if (!ir)
>  		goto fail;
> -- 
> 2.43.0
>

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