CVE-2008-1367 in gcc
Summary
by MITRE
gcc 4.3.x does not generate a cld instruction while compiling functions used for string manipulation such as memcpy and memmove on x86 and i386, which can prevent the direction flag (DF) from being reset in violation of ABI conventions and cause data to be copied in the wrong direction during signal handling in the Linux kernel, which might allow context-dependent attackers to trigger memory corruption. NOTE: this issue was originally reported for CPU consumption in SBCL.
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Analysis
by VulDB Data Team • 08/09/2019
The vulnerability described in CVE-2008-1367 represents a critical compliance failure in the GNU Compiler Collection version 4.3.x when targeting x86 and i386 architectures. This issue stems from the compiler's failure to properly generate the clear direction flag (cld) instruction during the compilation of string manipulation functions such as memcpy and memmove. The direction flag plays a fundamental role in x86 processor operation as it determines the direction of string operations, either incrementing or decrementing memory addresses during data movement. When this flag is not properly cleared, it can lead to unpredictable behavior in subsequent operations that depend on the flag's state.
The technical flaw manifests in the violation of Application Binary Interface (ABI) conventions that strictly require string manipulation functions to leave the direction flag in a known state. Specifically, the cld instruction is essential for clearing the direction flag, ensuring that string operations proceed in the correct direction regardless of the processor state when the function is called. When gcc 4.3.x omits this instruction, it creates a scenario where the direction flag retains its previous value, potentially causing memory operations to proceed in reverse direction. This behavior directly conflicts with the Linux kernel's signal handling mechanisms, which assume proper flag state management when executing code that may be interrupted by signals.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially enable memory corruption attacks. During signal handling in the Linux kernel, the processor state including the direction flag must be predictable and consistent. When the direction flag is improperly set due to compiler-generated code, memory copying operations can traverse memory in unintended directions, leading to data corruption, memory overwrite conditions, or potentially exploitable states. The vulnerability's original reporting in the context of CPU consumption in SBCL (Steel Bank Common Lisp) highlights how this issue can manifest in various software environments, particularly those heavily dependent on string manipulation functions and signal handling.
This vulnerability aligns with CWE-681 and CWE-122 categories, representing a misinterpretation of data direction and potential buffer overflow conditions. The issue also maps to ATT&CK technique T1059.007 for compiler-based attacks and T1070.006 for obfuscation through instruction manipulation. The flaw demonstrates how seemingly minor compiler optimizations or omissions can create fundamental security vulnerabilities in system-level operations. The vulnerability's exploitation potential increases when combined with other memory corruption issues, as attackers can leverage the unpredictable direction flag behavior to manipulate memory access patterns during signal delivery. Organizations should prioritize updating to compiler versions that properly implement the cld instruction for string operations, while system administrators should monitor for any unusual memory behavior or performance degradation that might indicate this vulnerability's presence in their environments.