Description

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...

Classification

CVE ID: CVE-2023-52894

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.06% (scored less or equal to compared to others)

EPSS Date: 2025-02-03 (when was this score calculated)

References

https://git.kernel.org/stable/c/fef6b29671b66dfb71f17e337c1ad14b5a2cedae
https://git.kernel.org/stable/c/63d161f29cd39c050e8873aa36e0c9fc013bb763
https://git.kernel.org/stable/c/a21da7f7aae618c785f7e4a275d43c06dc8412b6
https://git.kernel.org/stable/c/e92c70059178da751e5af7de02384b7dfadb5ec7
https://git.kernel.org/stable/c/a69c8dfb85b44be9cc223be07d35cc3a9baefbea
https://git.kernel.org/stable/c/09e4507ec8ef2d44da6ba4092b8ee2d81f216497
https://git.kernel.org/stable/c/c6ec929595c7443250b2a4faea988c62019d5cd2

Timeline