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elf: Allow arch to tweak initial mmap prot flags

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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 <broonie@kernel.org>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Dave Martin 2020-03-16 16:50:46 +00:00 committed by Catalin Marinas
parent 8ef8f360cf
commit fe0f67660e
3 changed files with 27 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/Kconfig.binfmt
View File

@ -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

18
fs/binfmt_elf.c
View File

@ -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

12
include/linux/elf.h
View File

@ -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 */