livepatch/core: Revert module_enable_ro and module_disable_ro

hulk inclusion
category: feature
bugzilla: 51921
CVE: NA

---------------------------

After commit d556e1b ("livepatch: Remove module_disable_ro() usage")
and commit 0d9fbf7 ("module: Remove module_disable_ro()") and
commit e6eff43 ("module: Make module_enable_ro() static again") merged,
the module_disable_ro is removed and module_enable_ro is make static.

It's ok for x86/ppc platform because the livepatch module relocation is
done by text poke func which internally modify the text addr by remap
to high virtaddr which has write permission.

However for arm/arm64 platform, it's apply_relocate[_add] still directly
modify the text code so we should change the module text permission before
relocation. Otherwise it will lead to following problem:

  Unable to handle kernel write to read-only memory at virtual address ffff800008a95288
  Mem abort info:
  ESR = 0x9600004f
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  Data abort info:
  ISV = 0, ISS = 0x0000004f
  CM = 0, WnR = 1
  swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000004133c000
  [ffff800008a95288] pgd=00000000bdfff003, p4d=00000000bdfff003, pud=00000000bdffe003,
		     pmd=0000000080ce7003, pte=0040000080d5d783
  Internal error: Oops: 9600004f [AmpereComputing#1] PREEMPT SMP
  Modules linked in: livepatch_testmod_drv(OK+) testmod_drv(O)
  CPU: 0 PID: 139 Comm: insmod Tainted: G           O  K   5.10.0-01131-gf6b4602e09b2-dirty AmpereComputing#35
  Hardware name: linux,dummy-virt (DT)
  pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--)
  pc : reloc_insn_imm+0x54/0x78
  lr : reloc_insn_imm+0x50/0x78
  sp : ffff800011cf3910
  ...
  Call trace:
   reloc_insn_imm+0x54/0x78
   apply_relocate_add+0x464/0x680
   klp_apply_section_relocs+0x11c/0x148
   klp_enable_patch+0x338/0x998
   patch_init+0x338/0x1000 [livepatch_testmod_drv]
   do_one_initcall+0x60/0x1d8
   do_init_module+0x58/0x1e0
   load_module+0x1fb4/0x2688
   __do_sys_finit_module+0xc0/0x128
   __arm64_sys_finit_module+0x20/0x30
   do_el0_svc+0x84/0x1b0
   el0_svc+0x14/0x20
   el0_sync_handler+0x90/0xc8
   el0_sync+0x158/0x180
   Code: 2a0503e0 9ad42a73 97d6a499 91000673 (b90002a0)
   ---[ end trace 67dd2ef1203ed335 ]---

Though the permission change is not necessary to x86/ppc platform, consider
that the jump_label_register api may modify the text code either, we just
put the change handle here instead of putting it in arch-specific relocate.

Besides, the jump_label_module_nb callback called in jump_label_register
also maybe need motify the module code either, it sort and swap the jump
entries if necessary. So just disable ro before jump_label handling and
restore it back.

Signed-off-by: Dong Kai <[email protected]>

Signed-off-by: Ye Weihua <[email protected]>
Reviewed-by: Yang Jihong <[email protected]>
Signed-off-by: Zheng Zengkai <[email protected]>

include/linux/module.h

@@ -887,6 +887,14 @@ extern int module_sysfs_initialized;
 
 #define __MODULE_STRING(x) __stringify(x)
 
+#ifdef CONFIG_STRICT_MODULE_RWX
+extern void module_enable_ro(const struct module *mod, bool after_init);
+extern void module_disable_ro(const struct module *mod);
+#else
+static inline void module_enable_ro(const struct module *mod, bool after_init) { }
+static inline void module_disable_ro(const struct module *mod) { }
+#endif
+
 #ifdef CONFIG_GENERIC_BUG
 void module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *,
 			 struct module *);

kernel/livepatch/core.c

@@ -968,6 +968,7 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 	struct klp_func *func;
 	int ret;
 
+	module_disable_ro(patch->mod);
 	if (klp_is_module(obj)) {
 		/*
 		 * Only write module-specific relocations here
@@ -976,9 +977,12 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 		 * itself.
 		 */
 		ret = klp_apply_object_relocs(patch, obj);
-		if (ret)
+		if (ret) {
+			module_enable_ro(patch->mod, true);
 			return ret;
+		}
 	}
+	module_enable_ro(patch->mod, true);
 
 	klp_for_each_func(obj, func) {
 		ret = klp_find_object_symbol(obj->name, func->old_name,
@@ -1147,10 +1151,14 @@ static int klp_init_patch(struct klp_patch *patch)
 	}
 
 	set_mod_klp_rel_state(patch->mod, MODULE_KLP_REL_DONE);
+	module_disable_ro(patch->mod);
 	jump_label_apply_nops(patch->mod);
 	ret = jump_label_register(patch->mod);
-	if (ret)
+	if (ret) {
+		module_enable_ro(patch->mod, true);
 		goto out;
+	}
+	module_enable_ro(patch->mod, true);
 
 #ifdef CONFIG_LIVEPATCH_STOP_MACHINE_CONSISTENCY
 	klp_for_each_object(patch, obj)

kernel/module.c

@@ -2063,7 +2063,20 @@ static void frob_writable_data(const struct module_layout *layout,
 		   (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
 }
 
-static void module_enable_ro(const struct module *mod, bool after_init)
+/* livepatching wants to disable read-only so it can frob module. */
+void module_disable_ro(const struct module *mod)
+{
+	if (!rodata_enabled)
+		return;
+
+	frob_text(&mod->core_layout, set_memory_rw);
+	frob_rodata(&mod->core_layout, set_memory_rw);
+	frob_ro_after_init(&mod->core_layout, set_memory_rw);
+	frob_text(&mod->init_layout, set_memory_rw);
+	frob_rodata(&mod->init_layout, set_memory_rw);
+}
+
+void module_enable_ro(const struct module *mod, bool after_init)
 {
 	if (!rodata_enabled)
 		return;
@@ -2108,7 +2121,6 @@ static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
 
 #else /* !CONFIG_STRICT_MODULE_RWX */
 static void module_enable_nx(const struct module *mod) { }
-static void module_enable_ro(const struct module *mod, bool after_init) {}
 static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
 				       char *secstrings, struct module *mod)
 {