{"id":"CVE-2023-52894","summary":"usb: gadget: f_ncm: fix potential NULL ptr deref in ncm_bitrate()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_ncm: fix potential NULL ptr deref in ncm_bitrate()\n\nIn Google internal bug 265639009 we've received an (as yet) unreproducible\ncrash report from an aarch64 GKI 5.10.149-android13 running device.\n\nAFAICT the source code is at:\n  https://android.googlesource.com/kernel/common/+/refs/tags/ASB-2022-12-05_13-5.10\n\nThe call stack is:\n  ncm_close() -\u003e ncm_notify() -\u003e ncm_do_notify()\nwith the crash at:\n  ncm_do_notify+0x98/0x270\nCode: 79000d0b b9000a6c f940012a f9400269 (b9405d4b)\n\nWhich I believe disassembles to (I don't know ARM assembly, but it looks sane enough to me...):\n\n  // halfword (16-bit) store presumably to event-\u003ewLength (at offset 6 of struct usb_cdc_notification)\n  0B 0D 00 79    strh w11, [x8, #6]\n\n  // word (32-bit) store presumably to req-\u003eLength (at offset 8 of struct usb_request)\n  6C 0A 00 B9    str  w12, [x19, #8]\n\n  // x10 (NULL) was read here from offset 0 of valid pointer x9\n  // IMHO we're reading 'cdev-\u003egadget' and getting NULL\n  // gadget is indeed at offset 0 of struct usb_composite_dev\n  2A 01 40 F9    ldr  x10, [x9]\n\n  // loading req-\u003ebuf pointer, which is at offset 0 of struct usb_request\n  69 02 40 F9    ldr  x9, [x19]\n\n  // x10 is null, crash, appears to be attempt to read cdev-\u003egadget-\u003emax_speed\n  4B 5D 40 B9    ldr  w11, [x10, #0x5c]\n\nwhich seems to line up with ncm_do_notify() case NCM_NOTIFY_SPEED code fragment:\n\n  event-\u003ewLength = cpu_to_le16(8);\n  req-\u003elength = NCM_STATUS_BYTECOUNT;\n\n  /* SPEED_CHANGE data is up/down speeds in bits/sec */\n  data = req-\u003ebuf + sizeof *event;\n  data[0] = cpu_to_le32(ncm_bitrate(cdev-\u003egadget));\n\nMy analysis of registers and NULL ptr deref crash offset\n  (Unable to handle kernel NULL pointer dereference at virtual address 000000000000005c)\nheavily suggests that the crash is due to 'cdev-\u003egadget' being NULL when executing:\n  data[0] = cpu_to_le32(ncm_bitrate(cdev-\u003egadget));\nwhich calls:\n  ncm_bitrate(NULL)\nwhich then calls:\n  gadget_is_superspeed(NULL)\nwhich reads\n  ((struct usb_gadget *)NULL)-\u003emax_speed\nand hits a panic.\n\nAFAICT, if I'm counting right, the offset of max_speed is indeed 0x5C.\n(remember there's a GKI KABI reservation of 16 bytes in struct work_struct)\n\nIt's not at all clear to me how this is all supposed to work...\nbut returning 0 seems much better than panic-ing...","modified":"2026-04-02T09:43:27.097076Z","published":"2024-08-21T06:10:34.120Z","related":["SUSE-SU-2024:3190-1","SUSE-SU-2024:3209-1","SUSE-SU-2024:3227-1","SUSE-SU-2024:3408-1","SUSE-SU-2024:3483-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/52xxx/CVE-2023-52894.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/09e4507ec8ef2d44da6ba4092b8ee2d81f216497"},{"type":"WEB","url":"https://git.kernel.org/stable/c/63d161f29cd39c050e8873aa36e0c9fc013bb763"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a21da7f7aae618c785f7e4a275d43c06dc8412b6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a69c8dfb85b44be9cc223be07d35cc3a9baefbea"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c6ec929595c7443250b2a4faea988c62019d5cd2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e92c70059178da751e5af7de02384b7dfadb5ec7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fef6b29671b66dfb71f17e337c1ad14b5a2cedae"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/52xxx/CVE-2023-52894.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-52894"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"1650113888fe7b7e16604a5019c32dd3ddeb3af2"},{"fixed":"fef6b29671b66dfb71f17e337c1ad14b5a2cedae"},{"fixed":"63d161f29cd39c050e8873aa36e0c9fc013bb763"},{"fixed":"a21da7f7aae618c785f7e4a275d43c06dc8412b6"},{"fixed":"e92c70059178da751e5af7de02384b7dfadb5ec7"},{"fixed":"a69c8dfb85b44be9cc223be07d35cc3a9baefbea"},{"fixed":"09e4507ec8ef2d44da6ba4092b8ee2d81f216497"},{"fixed":"c6ec929595c7443250b2a4faea988c62019d5cd2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-52894.json"}}],"schema_version":"1.7.5"}