| Message ID | 20210501093558.7375-1-jackp@codeaurora.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | [v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints | expand |
Hi Felipe, I know it may still be early in the merge window but do you have any feedback for this? We have some internal testers getting hit by this use-after-free when enabling SLUB_DEBUG or KASAN enabled builds. This fix resolves the issue in those cases so was hoping for a review soon so we can eventually queue it up for stable too. (I sent V2 quickly after V1 but before the kernel bot caught my obvious blunder on V1. But I sent V2 as a threaded-reply, so not sure if that made this get buried in people's inboxes...) Thanks Jack On Sat, May 01, 2021 at 02:35:58AM -0700, Jack Pham wrote: > As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure > dynamically") the dwc3_gadget_release() was added which will free > the dwc->gadget structure upon the device's removal when > usb_del_gadget_udc() is called in dwc3_gadget_exit(). > > However, simply freeing the gadget results a dangling pointer > situation: the endpoints created in dwc3_gadget_init_endpoints() > have their dep->endpoint.ep_list members chained off the list_head > anchored at dwc->gadget->ep_list. Thus when dwc->gadget is freed, > the first dwc3_ep in the list now has a dangling prev pointer and > likewise for the next pointer of the dwc3_ep at the tail of the list. > The dwc3_gadget_free_endpoints() that follows will result in a > use-after-free when it calls list_del(). > > This was caught by enabling KASAN and performing a driver unbind. > The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown > callback for dwc3") also exposes this as a panic during shutdown. > > There are a few possibilities to fix this. One could be to perform > a list_del() of the gadget->ep_list itself which removes it from > the rest of the dwc3_ep chain. > > Another approach is what this patch does, by splitting up the > usb_del_gadget_udc() call into its separate "del" and "put" > components. This allows dwc3_gadget_free_endpoints() to be > called before the gadget is finally freed with usb_put_gadget(). > > Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically") > Signed-off-by: Jack Pham <jackp@codeaurora.org> > --- > v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart > when manually recomposing the patch) > > drivers/usb/dwc3/gadget.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c > index 6eab78f8a1a7..c7e5f5a07f3b 100644 > --- a/drivers/usb/dwc3/gadget.c > +++ b/drivers/usb/dwc3/gadget.c > @@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc) > > void dwc3_gadget_exit(struct dwc3 *dwc) > { > - usb_del_gadget_udc(dwc->gadget); > + usb_del_gadget(dwc->gadget); > dwc3_gadget_free_endpoints(dwc); > + usb_put_gadget(dwc->gadget); > dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce, > dwc->bounce_addr); > kfree(dwc->setup_buf); > -- > 2.24.0 >
On 21-05-01 02:35:58, Jack Pham wrote: > As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure > dynamically") the dwc3_gadget_release() was added which will free > the dwc->gadget structure upon the device's removal when > usb_del_gadget_udc() is called in dwc3_gadget_exit(). > > However, simply freeing the gadget results a dangling pointer > situation: the endpoints created in dwc3_gadget_init_endpoints() > have their dep->endpoint.ep_list members chained off the list_head > anchored at dwc->gadget->ep_list. Thus when dwc->gadget is freed, > the first dwc3_ep in the list now has a dangling prev pointer and > likewise for the next pointer of the dwc3_ep at the tail of the list. > The dwc3_gadget_free_endpoints() that follows will result in a > use-after-free when it calls list_del(). > > This was caught by enabling KASAN and performing a driver unbind. > The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown > callback for dwc3") also exposes this as a panic during shutdown. > > There are a few possibilities to fix this. One could be to perform > a list_del() of the gadget->ep_list itself which removes it from > the rest of the dwc3_ep chain. > > Another approach is what this patch does, by splitting up the > usb_del_gadget_udc() call into its separate "del" and "put" > components. This allows dwc3_gadget_free_endpoints() to be > called before the gadget is finally freed with usb_put_gadget(). > > Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically") > Signed-off-by: Jack Pham <jackp@codeaurora.org> > --- > v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart > when manually recomposing the patch) > > drivers/usb/dwc3/gadget.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c > index 6eab78f8a1a7..c7e5f5a07f3b 100644 > --- a/drivers/usb/dwc3/gadget.c > +++ b/drivers/usb/dwc3/gadget.c > @@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc) > > void dwc3_gadget_exit(struct dwc3 *dwc) > { > - usb_del_gadget_udc(dwc->gadget); > + usb_del_gadget(dwc->gadget); > dwc3_gadget_free_endpoints(dwc); > + usb_put_gadget(dwc->gadget); > dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce, > dwc->bounce_addr); > kfree(dwc->setup_buf); > -- Reviewed-by: Peter Chen <peter.chen@kernel.org>
Hi, Jack Pham <jackp@codeaurora.org> writes: > As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure > dynamically") the dwc3_gadget_release() was added which will free > the dwc->gadget structure upon the device's removal when > usb_del_gadget_udc() is called in dwc3_gadget_exit(). > > However, simply freeing the gadget results a dangling pointer > situation: the endpoints created in dwc3_gadget_init_endpoints() > have their dep->endpoint.ep_list members chained off the list_head > anchored at dwc->gadget->ep_list. Thus when dwc->gadget is freed, > the first dwc3_ep in the list now has a dangling prev pointer and > likewise for the next pointer of the dwc3_ep at the tail of the list. > The dwc3_gadget_free_endpoints() that follows will result in a > use-after-free when it calls list_del(). > > This was caught by enabling KASAN and performing a driver unbind. > The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown > callback for dwc3") also exposes this as a panic during shutdown. > > There are a few possibilities to fix this. One could be to perform > a list_del() of the gadget->ep_list itself which removes it from > the rest of the dwc3_ep chain. > > Another approach is what this patch does, by splitting up the > usb_del_gadget_udc() call into its separate "del" and "put" > components. This allows dwc3_gadget_free_endpoints() to be > called before the gadget is finally freed with usb_put_gadget(). > > Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically") > Signed-off-by: Jack Pham <jackp@codeaurora.org> > --- > v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart > when manually recomposing the patch) I thought I had acked this one already, looks like I missed it: Acked-by: Felipe Balbi <balbi@kernel.org>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 6eab78f8a1a7..c7e5f5a07f3b 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc) void dwc3_gadget_exit(struct dwc3 *dwc) { - usb_del_gadget_udc(dwc->gadget); + usb_del_gadget(dwc->gadget); dwc3_gadget_free_endpoints(dwc); + usb_put_gadget(dwc->gadget); dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce, dwc->bounce_addr); kfree(dwc->setup_buf);
As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically") the dwc3_gadget_release() was added which will free the dwc->gadget structure upon the device's removal when usb_del_gadget_udc() is called in dwc3_gadget_exit(). However, simply freeing the gadget results a dangling pointer situation: the endpoints created in dwc3_gadget_init_endpoints() have their dep->endpoint.ep_list members chained off the list_head anchored at dwc->gadget->ep_list. Thus when dwc->gadget is freed, the first dwc3_ep in the list now has a dangling prev pointer and likewise for the next pointer of the dwc3_ep at the tail of the list. The dwc3_gadget_free_endpoints() that follows will result in a use-after-free when it calls list_del(). This was caught by enabling KASAN and performing a driver unbind. The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown callback for dwc3") also exposes this as a panic during shutdown. There are a few possibilities to fix this. One could be to perform a list_del() of the gadget->ep_list itself which removes it from the rest of the dwc3_ep chain. Another approach is what this patch does, by splitting up the usb_del_gadget_udc() call into its separate "del" and "put" components. This allows dwc3_gadget_free_endpoints() to be called before the gadget is finally freed with usb_put_gadget(). Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically") Signed-off-by: Jack Pham <jackp@codeaurora.org> --- v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart when manually recomposing the patch) drivers/usb/dwc3/gadget.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)