{"id":"CVE-2026-98764","title":"usb: gadget: f_fs: Fix NULL pointer dereference in FUNCTIONFS_ENDPOINT_DESC","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Fix NULL pointer dereference in FUNCTIONFS_ENDPOINT_DESC\n\nWhen user space sets up FunctionFS with only full-speed descriptors\n(e.g., flags = FUNCTION…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 9d8761b3c133f6c6a6d3486839dac60e2cf4bfe3","Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 7811d8e26c77f8eea79e22d0d14c67ec0658b348","Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 35ab269602e1f7c4c0fe6ea3477264bea77eced3","Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 9cd072788c76595529eb38f42bf94d23852f8534","Linux 3.18"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:47:56.225Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98764","references":[{"url":"https://git.kernel.org/stable/c/9d8761b3c133f6c6a6d3486839dac60e2cf4bfe3"},{"url":"https://git.kernel.org/stable/c/7811d8e26c77f8eea79e22d0d14c67ec0658b348"},{"url":"https://git.kernel.org/stable/c/35ab269602e1f7c4c0fe6ea3477264bea77eced3"},{"url":"https://git.kernel.org/stable/c/9cd072788c76595529eb38f42bf94d23852f8534"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T16:47:32.494Z","slug":"CVE-2026-98764","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Fix NULL pointer dereference in FUNCTIONFS_ENDPOINT_DESC\n\nWhen user space sets up FunctionFS with only full-speed descriptors\n(e.g., flags = FUNCTIONFS_HAS_FS_DESC) and the gadget operates at a\nhigher speed (such as USB_SPEED_HIGH or USB_SPEED_SUPER),\nconfig_ep_by_speed() detects that the function lacks descriptors for\nthe current speed, logs a warning, and falls back to full-speed\ndescriptors. The endpoint is then successfully enabled via\nusb_ep_enable(), and epfile->ep becomes valid.\n\nHowever, when user space subsequently issues the FUNCTIONFS_ENDPOINT_DESC\nioctl to query the endpoint descriptor, ffs_epfile_ioctl() selects the\ndescriptor index solely based on gadget->speed:\n\n\tswitch (epfile->ffs->gadget->speed) {\n\tcase USB_SPEED_SUPER:\n\tcase USB_SPEED_SUPER_PLUS:\n\t\tdesc_idx = 2;\n\t\tbreak;\n\tcase USB_SPEED_HIGH:\n\t\tdesc_idx = 1;\n\t\tbreak;\n\tdefault:\n\t\tdesc_idx = 0;\n\t}\n\tdesc = epfile->ep->descs[desc_idx];\n\tmemcpy(&desc1, desc, desc->bLength);\n\nBecause user space only supplied full-speed descriptors,\nepfile->ep->descs[1] is NULL. Dereferencing desc->bLength triggers an\nimmediate kernel NULL pointer dereference panic.\n\nFix this by falling back through lower speed descriptors if the current\nspeed descriptor was not supplied, matching the fallback logic in\nconfig_ep_by_speed() and historical f_fs behavior. If still missing,\nfall back to epfile->ep->ep->desc (the active descriptor), and return\n-EINVAL safely if no valid descriptor is found. In addition, mark desc\nas const to match struct usb_ep::desc and avoid discarding qualifiers.\n\n## Affected\n\n- `Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 9d8761b3c133f6c6a6d3486839dac60e2cf4bfe3`\n- `Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 7811d8e26c77f8eea79e22d0d14c67ec0658b348`\n- `Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 35ab269602e1f7c4c0fe6ea3477264bea77eced3`\n- `Linux >= c559a353410939c0884e83bdb0e2420a986ac53b < 9cd072788c76595529eb38f42bf94d23852f8534`\n- `Linux 3.18`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}