Date: Fri, 20 Nov 2015 11:45:05 +0100 From: Florian Weimer <fweimer@...hat.com> To: oss-security@...ts.openwall.com Subject: Instruction encoding which prevents execution of a suffix Suppose you have some critical kernel operation you want to protect against execution if some preconditions are not met. Therefore, you check the precondition, and abort if it is not met. But this does not really work because if attackers have control over the program counter, they can just enter the function after the checks. What generic transformations exist (on x86_64) to make sure that an attacker cannot jump over the checks and execute only a suffix of the function? I know of one approach—move the check into the kernel, before the critical operation—but this is not always desirable for architectural reasons. I'd also prefer solutions which do not require changing *all* indirect jumps in the process image, and something that does not involve dynamic code generation (JIT). Florian
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