Multiple integer overflows in the 32bit emulation for AMD64 architectures in Linux 2.4 kernel before 2.4.21 allows attackers to cause a denial of service or gain root privileges via unspecified vectors that trigger copy_from_user function calls with improper length arguments.
Critical vulnerability in older Linux kernels (2.4.x) allows for privilege escalation and denial-of-service attacks. Exploiting integer overflows in the AMD64 32-bit emulation, attackers can manipulate memory copy operations to overwrite critical kernel data, leading to system compromise. This vulnerability is a significant risk for systems still running vulnerable kernels.
Step 1: Target Selection: An attacker identifies a system running a vulnerable Linux kernel (2.4.x) with AMD64 architecture.
Step 2: Crafting the Payload: The attacker crafts a malicious 32-bit application designed to trigger the integer overflow. This application will make system calls that use copy_from_user with a carefully chosen length argument.
Step 3: Triggering the Overflow: The malicious application is executed on the target system. The crafted length argument, when used in calculations within the kernel's 32-bit emulation layer, causes an integer overflow.
Step 4: Memory Corruption: The overflowed length is used in subsequent memory copy operations. The copy_from_user function, using the wrapped-around length, copies data from user space into a kernel buffer, overflowing it.
Step 5: Privilege Escalation/DoS: The buffer overflow overwrites critical kernel data structures. This can lead to arbitrary code execution (privilege escalation) or a system crash (denial of service).
Root Cause: The vulnerability stems from multiple integer overflows within the 32-bit emulation layer of the Linux 2.4 kernel, specifically when handling memory copy operations using copy_from_user. The 32-bit emulation code, designed to allow 32-bit applications to run on 64-bit AMD64 architectures, incorrectly calculates the size of memory regions to be copied. This leads to an integer overflow, allowing a crafted 32-bit application to provide a large, malicious length argument to copy_from_user. This crafted length, after the integer overflow, wraps around to a small value. This small value is then used to allocate a buffer, but the original large value is used to copy data into the buffer. This results in a buffer overflow, potentially overwriting kernel data structures. The vulnerability is triggered by a crafted 32-bit application making system calls that utilize copy_from_user with the crafted length argument. The lack of proper bounds checking on the length argument allows for the overflow.