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module: Harden STRICT_MODULE_RWX 

We're very close to enforcing W^X memory, refuse to load modules that
violate this principle per construction.

[jeyu: move module_enforce_rwx_sections under STRICT_MODULE_RWX as per discussion]
Link: http://lore.kernel.org/r/20200403171303.GK20760@hirez.programming.kicks-ass.net
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
This commit is contained in:
Peter Zijlstra 2020-04-03 19:13:03 +02:00 committed by Jessica Yu
parent db991af02f
commit 5c3a7db0c7
1 changed files with 24 additions and 0 deletions
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24
kernel/module.c
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@ -2052,9 +2052,28 @@ static void module_enable_nx(const struct module *mod)
frob_writable_data(&mod->init_layout, set_memory_nx);
}
static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
char *secstrings, struct module *mod)
{
const unsigned long shf_wx = SHF_WRITE|SHF_EXECINSTR;
int i;
for (i = 0; i < hdr->e_shnum; i++) {
if ((sechdrs[i].sh_flags & shf_wx) == shf_wx)
return -ENOEXEC;
}
return 0;
}
#else /* !CONFIG_STRICT_MODULE_RWX */
/* module_{enable,disable}_ro() stubs are in module.h */
static void module_enable_nx(const struct module *mod) { }
static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
char *secstrings, struct module *mod)
{
return 0;
}
#endif /* CONFIG_STRICT_MODULE_RWX */
#ifdef CONFIG_LIVEPATCH
@ -3385,6 +3404,11 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
if (err < 0)
return ERR_PTR(err);
err = module_enforce_rwx_sections(info->hdr, info->sechdrs,
info->secstrings, info->mod);
if (err < 0)
return ERR_PTR(err);
/* We will do a special allocation for per-cpu sections later. */
info->sechdrs[info->index.pcpu].sh_flags &= ~(unsigned long)SHF_ALLOC;