From: Maciej Żenczykowski maze@google.com
commit 032e288097a553db5653af552dd8035cd2a0ba96 upstream.
usb_assign_descriptors() is called with 5 parameters, the last 4 of which are the usb_descriptor_header for: full-speed (USB1.1 - 12Mbps [including USB1.0 low-speed @ 1.5Mbps), high-speed (USB2.0 - 480Mbps), super-speed (USB3.0 - 5Gbps), super-speed-plus (USB3.1 - 10Gbps).
The differences between full/high/super-speed descriptors are usually substantial (due to changes in the maximum usb block size from 64 to 512 to 1024 bytes and other differences in the specs), while the difference between 5 and 10Gbps descriptors may be as little as nothing (in many cases the same tuning is simply good enough).
However if a gadget driver calls usb_assign_descriptors() with a NULL descriptor for super-speed-plus and is then used on a max 10gbps configuration, the kernel will crash with a null pointer dereference, when a 10gbps capable device port + cable + host port combination shows up. (This wouldn't happen if the gadget max-speed was set to 5gbps, but it of course defaults to the maximum, and there's no real reason to artificially limit it)
The fix is to simply use the 5gbps descriptor as the 10gbps descriptor, if a 10gbps descriptor wasn't provided.
Obviously this won't fix the problem if the 5gbps descriptor is also NULL, but such cases can't be so trivially solved (and any such gadgets are unlikely to be used with USB3 ports any way).
Cc: Felipe Balbi balbi@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Maciej Żenczykowski maze@google.com Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/20210609024459.1126080-1-zenczykowski@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/gadget/config.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/drivers/usb/gadget/config.c +++ b/drivers/usb/gadget/config.c @@ -164,6 +164,14 @@ int usb_assign_descriptors(struct usb_fu { struct usb_gadget *g = f->config->cdev->gadget;
+ /* super-speed-plus descriptor falls back to super-speed one, + * if such a descriptor was provided, thus avoiding a NULL + * pointer dereference if a 5gbps capable gadget is used with + * a 10gbps capable config (device port + cable + host port) + */ + if (!ssp) + ssp = ss; + if (fs) { f->fs_descriptors = usb_copy_descriptors(fs); if (!f->fs_descriptors)