>From ee5765a839f6a40a61960264ed46393dc5d6c534 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Mon, 13 Jul 2020 11:28:18 +0100 Subject: [PATCH] aarch64: Respect p_flags when protecting code with PROT_BTI Use PROT_READ and PROT_WRITE according to the load segment p_flags when adding PROT_BTI. This is before processing relocations which may drop PROT_BTI in case of textrels. Executable stacks are not protected via PROT_BTI either. PROT_BTI is hardening in case memory corruption happened, it's value is reduced if there is writable and executable memory available so missing it on such memory is fine, but we should respect the p_flags and should not drop PROT_WRITE. --- sysdeps/aarch64/dl-bti.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/sysdeps/aarch64/dl-bti.c b/sysdeps/aarch64/dl-bti.c index 965ddcc732..01ffb69a4a 100644 --- a/sysdeps/aarch64/dl-bti.c +++ b/sysdeps/aarch64/dl-bti.c @@ -24,13 +24,20 @@ static int enable_bti (struct link_map *map, const char *program) { const ElfW(Phdr) *phdr; - unsigned prot = PROT_READ | PROT_EXEC | PROT_BTI; + unsigned prot; for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr) if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X)) { void *start = (void *) (phdr->p_vaddr + map->l_addr); size_t len = phdr->p_memsz; + + prot = PROT_EXEC | PROT_BTI; + if (ph->p_flags & PF_R) + prot |= PROT_READ; + if (ph->p_flags & PF_W) + prot |= PROT_WRITE; + if (__mprotect (start, len, prot) < 0) { if (program) -- 2.17.1