From mboxrd@z Thu Jan 1 00:00:00 1970 Reply-To: kernel-hardening@lists.openwall.com From: Kees Cook Date: Wed, 17 Feb 2016 14:41:11 -0800 Message-Id: <1455748879-21872-1-git-send-email-keescook@chromium.org> Subject: [kernel-hardening] [PATCH v5 0/7] introduce post-init read-only memory To: Ingo Molnar Cc: Kees Cook , David Brown , Andy Lutomirski , "H. Peter Anvin" , Michael Ellerman , Mathias Krause , Thomas Gleixner , x86@kernel.org, Arnd Bergmann , PaX Team , Emese Revfy , kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, linux-arch List-ID: 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 and arm 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 v5: - rebased on linux-next (strtobool in -next, x86 vdso merge fixup) - added ARM vDSO patch, david.brown v4: - adjust documentation for strtobool, andy.shevchenko 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