From fe0f67660ee9c99408be5261ae045f8b41953b05 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Mon, 16 Mar 2020 16:50:46 +0000 Subject: [PATCH] elf: Allow arch to tweak initial mmap prot flags An arch may want to tweak the mmap prot flags for an ELFexecutable's initial mappings. For example, arm64 is going to need to add PROT_BTI for executable pages in an ELF process whose executable is marked as using Branch Target Identification (an ARMv8.5-A control flow integrity feature). So that this can be done in a generic way, add a hook arch_elf_adjust_prot() to modify the prot flags as desired: arches can select CONFIG_HAVE_ELF_PROT and implement their own backend where necessary. By default, leave the prot flags unchanged. Signed-off-by: Mark Brown Signed-off-by: Dave Martin Reviewed-by: Catalin Marinas Reviewed-by: Kees Cook Signed-off-by: Catalin Marinas --- fs/Kconfig.binfmt | 3 +++ fs/binfmt_elf.c | 18 ++++++++++++------ include/linux/elf.h | 12 ++++++++++++ 3 files changed, 27 insertions(+), 6 deletions(-) diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt index d2cfe0729a73fe..2358368319b8a0 100644 --- a/fs/Kconfig.binfmt +++ b/fs/Kconfig.binfmt @@ -36,6 +36,9 @@ config COMPAT_BINFMT_ELF config ARCH_BINFMT_ELF_STATE bool +config ARCH_HAVE_ELF_PROT + bool + config ARCH_USE_GNU_PROPERTY bool diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 1fb67e506b68b9..cceb29d6ef1d9f 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -544,7 +544,8 @@ static inline int arch_check_elf(struct elfhdr *ehdr, bool has_interp, #endif /* !CONFIG_ARCH_BINFMT_ELF_STATE */ -static inline int make_prot(u32 p_flags) +static inline int make_prot(u32 p_flags, struct arch_elf_state *arch_state, + bool has_interp, bool is_interp) { int prot = 0; @@ -554,7 +555,8 @@ static inline int make_prot(u32 p_flags) prot |= PROT_WRITE; if (p_flags & PF_X) prot |= PROT_EXEC; - return prot; + + return arch_elf_adjust_prot(prot, arch_state, has_interp, is_interp); } /* This is much more generalized than the library routine read function, @@ -564,7 +566,8 @@ static inline int make_prot(u32 p_flags) static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, struct file *interpreter, - unsigned long no_base, struct elf_phdr *interp_elf_phdata) + unsigned long no_base, struct elf_phdr *interp_elf_phdata, + struct arch_elf_state *arch_state) { struct elf_phdr *eppnt; unsigned long load_addr = 0; @@ -596,7 +599,8 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, for (i = 0; i < interp_elf_ex->e_phnum; i++, eppnt++) { if (eppnt->p_type == PT_LOAD) { int elf_type = MAP_PRIVATE | MAP_DENYWRITE; - int elf_prot = make_prot(eppnt->p_flags); + int elf_prot = make_prot(eppnt->p_flags, arch_state, + true, true); unsigned long vaddr = 0; unsigned long k, map_addr; @@ -1041,7 +1045,8 @@ static int load_elf_binary(struct linux_binprm *bprm) } } - elf_prot = make_prot(elf_ppnt->p_flags); + elf_prot = make_prot(elf_ppnt->p_flags, &arch_state, + !!interpreter, false); elf_flags = MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE; @@ -1184,7 +1189,8 @@ static int load_elf_binary(struct linux_binprm *bprm) if (interpreter) { elf_entry = load_elf_interp(&loc->interp_elf_ex, interpreter, - load_bias, interp_elf_phdata); + load_bias, interp_elf_phdata, + &arch_state); if (!IS_ERR((void *)elf_entry)) { /* * load_elf_interp() returns relocation diff --git a/include/linux/elf.h b/include/linux/elf.h index db5113479f5e93..5d5b0321da0bd8 100644 --- a/include/linux/elf.h +++ b/include/linux/elf.h @@ -87,4 +87,16 @@ extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, struct arch_elf_state *arch); #endif +#ifdef CONFIG_ARCH_HAVE_ELF_PROT +int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state, + bool has_interp, bool is_interp); +#else +static inline int arch_elf_adjust_prot(int prot, + const struct arch_elf_state *state, + bool has_interp, bool is_interp) +{ + return prot; +} +#endif + #endif /* _LINUX_ELF_H */