CVE-2023-52894

published 2024-08-21

CVE-2023-52894: 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…

Priority P4 21 medium 5.5 CVSS 3.1

AV L AC L PR L UI N S U C N I N A H

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

Affected

20 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 6.1.8-1 (bookworm)	linux 6.1.8-1 (bookworm)
linux	linux	—	—
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < fef6b29671b66dfb71f17e337c1ad14b5a2cedae	fef6b29671b66dfb71f17e337c1ad14b5a2cedae
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < 63d161f29cd39c050e8873aa36e0c9fc013bb763	63d161f29cd39c050e8873aa36e0c9fc013bb763
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < a21da7f7aae618c785f7e4a275d43c06dc8412b6	a21da7f7aae618c785f7e4a275d43c06dc8412b6
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < e92c70059178da751e5af7de02384b7dfadb5ec7	e92c70059178da751e5af7de02384b7dfadb5ec7
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < a69c8dfb85b44be9cc223be07d35cc3a9baefbea	a69c8dfb85b44be9cc223be07d35cc3a9baefbea
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < 09e4507ec8ef2d44da6ba4092b8ee2d81f216497	09e4507ec8ef2d44da6ba4092b8ee2d81f216497
linux	linux	>= 1650113888fe7b7e16604a5019c32dd3ddeb3af2 < c6ec929595c7443250b2a4faea988c62019d5cd2	c6ec929595c7443250b2a4faea988c62019d5cd2
linux	linux_kernel	< 4.14.304	4.14.304
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 5.10.178-1	5.10.178-1
linux	linux_kernel	>= 0 < 6.1.8-1	6.1.8-1
linux	linux_kernel	>= 0 < 6.1.8-1	6.1.8-1
linux	linux_kernel	>= 0 < 6.1.8-1	6.1.8-1
linux	linux_kernel	>= 4.15 < 4.19.271	4.19.271
linux	linux_kernel	>= 4.20 < 5.4.230	5.4.230
linux	linux_kernel	>= 5.11 < 5.15.90	5.15.90
linux	linux_kernel	>= 5.16 < 6.1.8	6.1.8
linux	linux_kernel	>= 5.5 < 5.10.165	5.10.165

CVSS provenance

nvd v3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv 5.5 MEDIUM

vendor_debian 5.5 MEDIUM

vendor_redhat 5.5 MEDIUM

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