From 7ebd114211dcd290efd54e610bbde0765bd7764c 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..196e462520 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 (phdr->p_flags & PF_R) + prot |= PROT_READ; + if (phdr->p_flags & PF_W) + prot |= PROT_WRITE; + if (__mprotect (start, len, prot) < 0) { if (program) -- 2.43.5