Deployments of BTI on arm64 have run into issues interacting with systemd's MemoryDenyWriteExecute feature. Currently for dynamically linked executables the kernel will only handle architecture specific properties like BTI for the interpreter, the expectation is that the interpreter will then handle any properties on the main executable. For BTI this means remapping the executable segments PROT_EXEC | PROT_BTI. This interacts poorly with MemoryDenyWriteExecute since that is implemented using a seccomp filter which prevents setting PROT_EXEC on already mapped memory and lacks the context to be able to detect that memory is already mapped with PROT_EXEC. This series resolves this by handling the BTI property for both the interpreter and the main executable. This does mean that we may get more code with BTI enabled if running on a system without BTI support in the dynamic linker, this is expected to be a safe configuration and testing seems to confirm that. It also reduces the flexibility userspace has to disable BTI but it is expected that for cases where there are problems which require BTI to be disabled it is more likely that it will need to be disabled on a system level. Mark Brown (2): elf: Allow architectures to parse properties on the main executable arm64: Enable BTI for main executable as well as the interpreter arch/arm64/include/asm/elf.h | 13 ++++++++++--- arch/arm64/kernel/process.c | 18 ++++++------------ fs/binfmt_elf.c | 25 +++++++++++++++++-------- include/linux/elf.h | 4 +++- 4 files changed, 36 insertions(+), 24 deletions(-) base-commit: d07f6ca923ea0927a1024dfccafc5b53b61cfecc -- 2.20.1
