Linux Kernel Arm64 Compatibility Syscall Handling Vulnerability

A vulnerability in the Linux kernel's handling of compatibility system calls for arm64 processes has been addressed. When a compatibility process attempts to execute an unknown system call above the __ARM_NR_COMPAT_END threshold, the kernel responds by sending a SIGILL signal to the process. However, the error reporting mechanism inadvertently misinterprets the syscall number as an exception syndrome value, leading to the display of incorrect error messages. This issue arises because the compatibility syscall handler does not properly validate syscall numbers, allowing invalid values to be processed incorrectly. The vulnerability could be exploited by a compatibility process that sends a syscall number interpreted as negative, bypassing normal error handling and causing the kernel to print misleading exception information.

Impact

Exploitation of this vulnerability could result in the kernel providing false error reports about system call exceptions, potentially misleading developers or system administrators.