CVE-2023-53986
Unknown Unknown - Not Provided
Kernel Panic Due to RAC Flush Vulnerability in BCM6358 MIPS

Publication date: 2025-12-24

Last updated on: 2025-12-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: mips: bmips: BCM6358: disable RAC flush for TP1 RAC flush causes kernel panics on BCM6358 with EHCI/OHCI when booting from TP1: [ 3.881739] usb 1-1: new high-speed USB device number 2 using ehci-platform [ 3.895011] Reserved instruction in kernel code[#1]: [ 3.900113] CPU: 0 PID: 1 Comm: init Not tainted 5.10.16 #0 [ 3.905829] $ 0 : 00000000 10008700 00000000 77d94060 [ 3.911238] $ 4 : 7fd1f088 00000000 81431cac 81431ca0 [ 3.916641] $ 8 : 00000000 ffffefff 8075cd34 00000000 [ 3.922043] $12 : 806f8d40 f3e812b7 00000000 000d9aaa [ 3.927446] $16 : 7fd1f068 7fd1f080 7ff559b8 81428470 [ 3.932848] $20 : 00000000 00000000 55590000 77d70000 [ 3.938251] $24 : 00000018 00000010 [ 3.943655] $28 : 81430000 81431e60 81431f28 800157fc [ 3.949058] Hi : 00000000 [ 3.952013] Lo : 00000000 [ 3.955019] epc : 80015808 setup_sigcontext+0x54/0x24c [ 3.960464] ra : 800157fc setup_sigcontext+0x48/0x24c [ 3.965913] Status: 10008703 KERNEL EXL IE [ 3.970216] Cause : 00800028 (ExcCode 0a) [ 3.974340] PrId : 0002a010 (Broadcom BMIPS4350) [ 3.979170] Modules linked in: ohci_platform ohci_hcd fsl_mph_dr_of ehci_platform ehci_fsl ehci_hcd gpio_button_hotplug usbcore nls_base usb_common [ 3.992907] Process init (pid: 1, threadinfo=(ptrval), task=(ptrval), tls=77e22ec8) [ 4.000776] Stack : 81431ef4 7fd1f080 81431f28 81428470 7fd1f068 81431edc 7ff559b8 81428470 [ 4.009467] 81431f28 7fd1f080 55590000 77d70000 77d5498c 80015c70 806f0000 8063ae74 [ 4.018149] 08100002 81431f28 0000000a 08100002 81431f28 0000000a 77d6b418 00000003 [ 4.026831] ffffffff 80016414 80080734 81431ecc 81431ecc 00000001 00000000 04000000 [ 4.035512] 77d54874 00000000 00000000 00000000 00000000 00000012 00000002 00000000 [ 4.044196] ... [ 4.046706] Call Trace: [ 4.049238] [<80015808>] setup_sigcontext+0x54/0x24c [ 4.054356] [<80015c70>] setup_frame+0xdc/0x124 [ 4.059015] [<80016414>] do_notify_resume+0x1dc/0x288 [ 4.064207] [<80011b50>] work_notifysig+0x10/0x18 [ 4.069036] [ 4.070538] Code: 8fc300b4 00001025 26240008 <ac820000> ac830004 3c048063 0c0228aa 24846a00 26240010 [ 4.080686] [ 4.082517] ---[ end trace 22a8edb41f5f983b ]--- [ 4.087374] Kernel panic - not syncing: Fatal exception [ 4.092753] Rebooting in 1 seconds.. Because the bootloader (CFE) is not initializing the Read-ahead cache properly on the second thread (TP1). Since the RAC was not initialized properly, we should avoid flushing it at the risk of corrupting the instruction stream as seen in the trace above.
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Meta Information
Published
2025-12-24
Last Modified
2025-12-24
Generated
2026-05-07
AI Q&A
2025-12-24
EPSS Evaluated
2026-05-05
NVD
CVE-2023-53986
EUVD
EUVD-2025-205156
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
broadcom bc6358 *
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel on the Broadcom BCM6358 platform. It is caused by the bootloader (CFE) not properly initializing the Read-ahead cache (RAC) on the second thread (TP1). When the kernel attempts to flush the RAC during boot with EHCI/OHCI USB controllers, it causes kernel panics due to corrupted instruction streams. The fix disables RAC flush for TP1 to prevent these panics.


How can this vulnerability impact me? :

If affected, this vulnerability can cause kernel panics during system boot on devices using the Broadcom BCM6358 chipset with EHCI/OHCI USB controllers. This results in system instability and reboot loops, preventing the system from booting properly.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by observing kernel panic messages during boot on BCM6358 devices using EHCI/OHCI USB controllers. Specifically, look for kernel panic logs similar to the provided trace showing 'Reserved instruction in kernel code' and messages related to 'setup_sigcontext' and 'Kernel panic - not syncing: Fatal exception'. Checking system logs (e.g., dmesg) for these panic traces can help detect the issue.


What immediate steps should I take to mitigate this vulnerability?

The immediate mitigation is to disable the RAC (Read-ahead cache) flush for the second thread (TP1) on BCM6358 devices, as the bootloader does not initialize the RAC properly on TP1. Avoid flushing the RAC to prevent kernel panics and instruction stream corruption. Applying the Linux kernel update that includes this fix is recommended.


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