CVE-2023-52894

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Source
https://nvd.nist.gov/vuln/detail/CVE-2023-52894
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-52894.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2023-52894
Related
Published
2024-08-21T07:15:05Z
Modified
2024-09-18T03:24:40.741497Z
Severity
  • 5.5 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
[none]
Details

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

usb: gadget: fncm: fix potential NULL ptr deref in ncmbitrate()

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: ncmclose() -> ncmnotify() -> ncmdonotify() with the crash at: ncmdonotify+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 usbcdcnotification) 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 usbcompositedev 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 ncmdonotify() case NCMNOTIFYSPEED code fragment:

event->wLength = cputole16(8); req->length = NCMSTATUSBYTECOUNT;

/* SPEEDCHANGE data is up/down speeds in bits/sec */ data = req->buf + sizeof *event; data[0] = cputole32(ncmbitrate(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] = cputole32(ncmbitrate(cdev->gadget)); which calls: ncmbitrate(NULL) which then calls: gadgetissuperspeed(NULL) which reads ((struct usbgadget *)NULL)->maxspeed and hits a panic.

AFAICT, if I'm counting right, the offset of maxspeed is indeed 0x5C. (remember there's a GKI KABI reservation of 16 bytes in struct workstruct)

It's not at all clear to me how this is all supposed to work... but returning 0 seems much better than panic-ing...

References

Affected packages

Debian:11 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
5.10.178-1

Affected versions

5.*

5.10.46-4
5.10.46-5
5.10.70-1~bpo10+1
5.10.70-1
5.10.84-1
5.10.92-1~bpo10+1
5.10.92-1
5.10.92-2
5.10.103-1~bpo10+1
5.10.103-1
5.10.106-1
5.10.113-1
5.10.120-1~bpo10+1
5.10.120-1
5.10.127-1
5.10.127-2~bpo10+1
5.10.127-2
5.10.136-1
5.10.140-1
5.10.148-1
5.10.149-1
5.10.149-2
5.10.158-1
5.10.158-2
5.10.162-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:12 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
6.1.8-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:13 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
6.1.8-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}