Messages in this thread | | | From | Kees Cook <> | Subject | [PATCH v3 0/8] introduce post-init read-only memory | Date | Wed, 9 Dec 2015 13:43:16 -0800 |
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One of the easiest ways to protect the kernel from attack is to reduce the internal attack surface exposed when a "write" flaw is available. By making as much of the kernel read-only as possible, we reduce the attack surface.
Many things are written to only during __init, and never changed again. These cannot be made "const" since the compiler will do the wrong thing (we do actually need to write to them). Instead, move these items into a memory region that will be made read-only during mark_rodata_ro() which happens after all kernel __init code has finished.
This introduces __ro_after_init as a way to mark such memory, and uses it on the x86 vDSO to kill an extant kernel exploitation method. Also adds a new kernel parameter to help debug future use and adds an lkdtm test to check the results.
-Kees
v3: - conslidated mark_rodata_ro() - make CONFIG_DEBUG_RODATA always enabled on x86, mingo - enhanced strtobool and potential callers to use "on"/"off" - use strtobool for rodata= param, gregkh v2: - renamed __read_only to __ro_after_init
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