Various routines for the ppc64 architecture on Linux kernel 2.6 prior to 2.6.2 and 2.4 prior to 2.4.24 do not use the copy_from_user function when copying data from userspace to kernelspace, which crosses security boundaries and allows local users to cause a denial of service.
Critical vulnerability in older Linux kernel versions (2.4 and 2.6 for ppc64 architecture) allows local users to achieve a denial-of-service (DoS) by exploiting a failure to properly validate user-supplied data. This flaw bypasses security boundaries, enabling malicious actors to potentially crash the system or corrupt kernel memory, leading to significant system instability.
Step 1: Triggering the Vulnerability: The attacker identifies a vulnerable kernel routine that copies data from userspace to kernelspace without using copy_from_user.
Step 2: Crafting the Malicious Input: The attacker crafts a malicious input, typically a specially crafted data structure or buffer, designed to exploit the missing validation.
Step 3: Providing the Input: The attacker provides the malicious input to the vulnerable kernel routine, often through a system call or device driver interface.
Step 4: Exploiting the Copy Operation: The kernel routine attempts to copy the attacker's input into kernel memory using a vulnerable copy operation (e.g., memcpy).
Step 5: Memory Corruption/DoS: Due to the lack of validation, the copy operation either overflows a kernel buffer, overwrites critical kernel data, or causes an invalid memory access, leading to a kernel panic and a DoS.
The vulnerability stems from the absence of the copy_from_user function in several kernel routines when handling data transfers from userspace to kernelspace on the ppc64 architecture. This function is crucial for validating the size and validity of user-provided data before it's copied into kernel memory. Without this check, attackers can provide oversized or malformed data, leading to a buffer overflow or other memory corruption issues. The specific flaw lies in the direct use of memory copy operations (e.g., memcpy) without proper bounds checking or validation of the source address provided by the user. This allows attackers to overwrite kernel memory, potentially corrupting critical data structures, causing a kernel panic, or leading to a DoS.