ghsa-9r79-4jhv-2rfr
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_ncm: fix potential NULL ptr deref in ncm_bitrate()
In Google internal bug 265639009 we've received an (as yet) unreproducible crash report from an aarch64 GKI 5.10.149-android13 running device.
AFAICT the source code is at: https://android.googlesource.com/kernel/common/+/refs/tags/ASB-2022-12-05_13-5.10
The call stack is: ncm_close() -> ncm_notify() -> ncm_do_notify() with the crash at: ncm_do_notify+0x98/0x270 Code: 79000d0b b9000a6c f940012a f9400269 (b9405d4b)
Which I believe disassembles to (I don't know ARM assembly, but it looks sane enough to me...):
// halfword (16-bit) store presumably to event->wLength (at offset 6 of struct usb_cdc_notification) 0B 0D 00 79 strh w11, [x8, #6]
// word (32-bit) store presumably to req->Length (at offset 8 of struct usb_request) 6C 0A 00 B9 str w12, [x19, #8]
// x10 (NULL) was read here from offset 0 of valid pointer x9 // IMHO we're reading 'cdev->gadget' and getting NULL // gadget is indeed at offset 0 of struct usb_composite_dev 2A 01 40 F9 ldr x10, [x9]
// loading req->buf pointer, which is at offset 0 of struct usb_request 69 02 40 F9 ldr x9, [x19]
// x10 is null, crash, appears to be attempt to read cdev->gadget->max_speed 4B 5D 40 B9 ldr w11, [x10, #0x5c]
which seems to line up with ncm_do_notify() case NCM_NOTIFY_SPEED code fragment:
event->wLength = cpu_to_le16(8); req->length = NCM_STATUS_BYTECOUNT;
/ SPEED_CHANGE data is up/down speeds in bits/sec / data = req->buf + sizeof *event; data[0] = cpu_to_le32(ncm_bitrate(cdev->gadget));
My analysis of registers and NULL ptr deref crash offset (Unable to handle kernel NULL pointer dereference at virtual address 000000000000005c) heavily suggests that the crash is due to 'cdev->gadget' being NULL when executing: data[0] = cpu_to_le32(ncm_bitrate(cdev->gadget)); which calls: ncm_bitrate(NULL) which then calls: gadget_is_superspeed(NULL) which reads ((struct usb_gadget *)NULL)->max_speed and hits a panic.
AFAICT, if I'm counting right, the offset of max_speed is indeed 0x5C. (remember there's a GKI KABI reservation of 16 bytes in struct work_struct)
It's not at all clear to me how this is all supposed to work... but returning 0 seems much better than panic-ing...
{
"affected": [],
"aliases": [
"CVE-2023-52894"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-08-21T07:15:05Z",
"severity": "MODERATE"
},
"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\u0027ve 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\u0027t 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\u0027re reading \u0027cdev-\u003egadget\u0027 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 \u0027cdev-\u003egadget\u0027 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\u0027m counting right, the offset of max_speed is indeed 0x5C.\n(remember there\u0027s a GKI KABI reservation of 16 bytes in struct work_struct)\n\nIt\u0027s not at all clear to me how this is all supposed to work...\nbut returning 0 seems much better than panic-ing...",
"id": "GHSA-9r79-4jhv-2rfr",
"modified": "2024-09-11T18:31:02Z",
"published": "2024-08-21T09:31:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-52894"
},
{
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.