NULL Pointer Dereference Affecting kernel-64kb package, versions <5.14.21-150500.55.80.2
Threat Intelligence
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Test your applications- Snyk IDSNYK-SLES155-KERNEL64KB-8105016
- published28 Sept 2024
- disclosed27 Sept 2024
Introduced: 27 Sep 2024
CVE-2023-52894 (opens in a new tab)How to fix?
Upgrade SLES:15.5 kernel-64kb to version 5.14.21-150500.55.80.2 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-64kb package and not the kernel-64kb package as distributed by SLES.
See How to fix? for SLES:15.5 relevant fixed versions and status.
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...
References
- https://www.suse.com/security/cve/CVE-2023-52894.html
- https://bugzilla.suse.com/1229566
- https://git.kernel.org/stable/c/09e4507ec8ef2d44da6ba4092b8ee2d81f216497
- https://git.kernel.org/stable/c/63d161f29cd39c050e8873aa36e0c9fc013bb763
- https://git.kernel.org/stable/c/a21da7f7aae618c785f7e4a275d43c06dc8412b6
- https://git.kernel.org/stable/c/a69c8dfb85b44be9cc223be07d35cc3a9baefbea
- https://git.kernel.org/stable/c/c6ec929595c7443250b2a4faea988c62019d5cd2
- https://git.kernel.org/stable/c/e92c70059178da751e5af7de02384b7dfadb5ec7
- https://git.kernel.org/stable/c/fef6b29671b66dfb71f17e337c1ad14b5a2cedae