CVE-2024-47742

In the Linux kernel, the following vulnerability has been resolved:

firmware_loader: Block path traversal

Most firmware names are hardcoded strings, or are constructed from fairly

constrained format strings where the dynamic parts are just some hex

numbers or such.

However, there are a couple codepaths in the kernel where firmware file

names contain string components that are passed through from a device or

semi-privileged userspace; the ones I could find (not counting interfaces

that require root privileges) are:

- lpfc_sli4_request_firmware_update() seems to construct the firmware

filename from "ModelName", a string that was previously parsed out of

some descriptor ("Vital Product Data") in lpfc_fill_vpd()

- nfp_net_fw_find() seems to construct a firmware filename from a model

name coming from nfp_hwinfo_lookup(pf->hwinfo, "nffw.partno"), which I

think parses some descriptor that was read from the device.

(But this case likely isn't exploitable because the format string looks

like "netronome/nic_%s", and there shouldn't be any *folders* starting

with "netronome/nic_". The previous case was different because there,

the "%s" is *at the start* of the format string.)

- module_flash_fw_schedule() is reachable from the

ETHTOOL_MSG_MODULE_FW_FLASH_ACT netlink command, which is marked as

GENL_UNS_ADMIN_PERM (meaning CAP_NET_ADMIN inside a user namespace is

enough to pass the privilege check), and takes a userspace-provided

firmware name.

(But I think to reach this case, you need to have CAP_NET_ADMIN over a

network namespace that a special kind of ethernet device is mapped into,

so I think this is not a viable attack path in practice.)

Fix it by rejecting any firmware names containing ".." path components.

For what it's worth, I went looking and haven't found any USB device

drivers that use the firmware loader dangerously.