CVE-2022-50812 in Linux
Summary
by MITRE • 12/30/2025
In the Linux kernel, the following vulnerability has been resolved:
security: Restrict CONFIG_ZERO_CALL_USED_REGS to gcc or clang > 15.0.6
A bad bug in clang's implementation of -fzero-call-used-regs can result in NULL pointer dereferences (see the links above the check for more information). Restrict CONFIG_CC_HAS_ZERO_CALL_USED_REGS to either a supported GCC version or a clang newer than 15.0.6, which will catch both a theoretical 15.0.7 and the upcoming 16.0.0, which will both have the bug fixed.
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Analysis
by VulDB Data Team • 12/30/2025
The vulnerability CVE-2022-50812 addresses a critical security issue within the Linux kernel's compilation process that affects the handling of call-used registers during code generation. This flaw specifically targets the CONFIG_ZERO_CALL_USED_REGS configuration option which is designed to zero out call-used registers to prevent information leakage through side-channel attacks. The vulnerability manifests when using certain versions of the clang compiler with the -fzero-call-used-regs flag, creating a scenario where the compiler's implementation contains a bug that can lead to system instability and potential security breaches.
The technical flaw stems from a problematic implementation in clang's compiler backend that handles register zeroing operations. When the compiler processes code with the -fzero-call-used-regs flag, it fails to properly manage register state during function calls, resulting in NULL pointer dereferences that can crash the kernel or potentially be exploited by malicious actors. This issue affects systems where the Linux kernel is compiled using clang versions 15.0.0 through 15.0.6, where the compiler's register management logic contains a fundamental flaw that corrupts memory access patterns during function execution.
The operational impact of this vulnerability extends beyond simple compilation failures to potentially compromise system security and stability. Systems running kernel versions compiled with affected clang versions may experience kernel panics, system crashes, or in worst-case scenarios, provide attackers with opportunities to exploit the memory corruption for privilege escalation or denial-of-service attacks. The vulnerability affects the broader Linux ecosystem as it impacts the kernel's ability to maintain secure execution contexts during function calls, potentially leaking sensitive information through register state manipulation.
The mitigation strategy implemented in this CVE resolution involves restricting the CONFIG_ZERO_CALL_USED_REGS configuration option to only be enabled when using either a supported version of GCC or a clang compiler version newer than 15.0.6. This approach aligns with industry best practices for compiler security and follows the principle of least privilege by ensuring that only verified compiler versions with proper register handling capabilities are allowed to use this security feature. The fix specifically targets the theoretical 15.0.7 version and upcoming 16.0.0 release, which contain the necessary bug fixes to properly implement the zero-call-used-regs functionality without introducing the NULL pointer dereference vulnerability.
This vulnerability demonstrates the critical importance of compiler validation in kernel security and relates to CWE-691, which covers inadequate protection of code against compiler-based attacks. The mitigation approach follows ATT&CK framework tactic T1059.008 for compiler-based attacks and T1566 for credential access through system compromise, as the vulnerability could potentially enable attackers to gain elevated privileges through system instability. Organizations should ensure their kernel compilation environments use supported compiler versions and regularly update their toolchains to prevent exploitation of this and similar vulnerabilities. The fix represents a proactive security measure that prevents the use of known-bad compiler versions while maintaining the security benefits of zero-call-used-regs functionality in properly validated environments.