2 files changed, 92 insertions, 55 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 40cfac8156fd..c02791e5c75b 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -191,12 +191,12 @@ static int klp_find_object_symbol(const char *objname, const char *name,
 	return -EINVAL;
 }
 
-static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
+static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
+			       unsigned int symndx, Elf_Shdr *relasec)
 {
 	int i, cnt, vmlinux, ret;
 	char objname[MODULE_NAME_LEN];
 	char symname[KSYM_NAME_LEN];
-	char *strtab = pmod->core_kallsyms.strtab;
 	Elf_Rela *relas;
 	Elf_Sym *sym;
 	unsigned long sympos, addr;
@@ -216,7 +216,7 @@ static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 	relas = (Elf_Rela *) relasec->sh_addr;
 	/* For each rela in this klp relocation section */
 	for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
-		sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
+		sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
 		if (sym->st_shndx != SHN_LIVEPATCH) {
 			pr_err("symbol %s is not marked as a livepatch symbol\n",
 			       strtab + sym->st_name);
@@ -246,54 +246,59 @@ static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 	return 0;
 }
 
-static int klp_write_object_relocations(struct module *pmod,
-					struct klp_object *obj)
+/*
+ * At a high-level, there are two types of klp relocation sections: those which
+ * reference symbols which live in vmlinux; and those which reference symbols
+ * which live in other modules.  This function is called for both types:
+ *
+ * 1) When a klp module itself loads, the module code calls this function to
+ *    write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
+ *    These relocations are written to the klp module text to allow the patched
+ *    code/data to reference unexported vmlinux symbols.  They're written as
+ *    early as possible to ensure that other module init code (.e.g.,
+ *    jump_label_apply_nops) can access any unexported vmlinux symbols which
+ *    might be referenced by the klp module's special sections.
+ *
+ * 2) When a to-be-patched module loads -- or is already loaded when a
+ *    corresponding klp module loads -- klp code calls this function to write
+ *    module-specific klp relocations (.klp.rela.{module}.* sections).  These
+ *    are written to the klp module text to allow the patched code/data to
+ *    reference symbols which live in the to-be-patched module or one of its
+ *    module dependencies.  Exported symbols are supported, in addition to
+ *    unexported symbols, in order to enable late module patching, which allows
+ *    the to-be-patched module to be loaded and patched sometime *after* the
+ *    klp module is loaded.
+ */
+int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
+			     const char *shstrtab, const char *strtab,
+			     unsigned int symndx, unsigned int secndx,
+			     const char *objname)
 {
-	int i, cnt, ret = 0;
-	const char *objname, *secname;
+	int cnt, ret;
 	char sec_objname[MODULE_NAME_LEN];
-	Elf_Shdr *sec;
+	Elf_Shdr *sec = sechdrs + secndx;
 
-	if (WARN_ON(!klp_is_object_loaded(obj)))
+	/*
+	 * Format: .klp.rela.sec_objname.section_name
+	 * See comment in klp_resolve_symbols() for an explanation
+	 * of the selected field width value.
+	 */
+	cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
+		     sec_objname);
+	if (cnt != 1) {
+		pr_err("section %s has an incorrectly formatted name\n",
+		       shstrtab + sec->sh_name);
 		return -EINVAL;
+	}
 
-	objname = klp_is_module(obj) ? obj->name : "vmlinux";
-
-	/* For each klp relocation section */
-	for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
-		sec = pmod->klp_info->sechdrs + i;
-		secname = pmod->klp_info->secstrings + sec->sh_name;
-		if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
-			continue;
-
-		/*
-		 * Format: .klp.rela.sec_objname.section_name
-		 * See comment in klp_resolve_symbols() for an explanation
-		 * of the selected field width value.
-		 */
-		cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
-		if (cnt != 1) {
-			pr_err("section %s has an incorrectly formatted name\n",
-			       secname);
-			ret = -EINVAL;
-			break;
-		}
-
-		if (strcmp(objname, sec_objname))
-			continue;
-
-		ret = klp_resolve_symbols(sec, pmod);
-		if (ret)
-			break;
+	if (strcmp(objname ? objname : "vmlinux", sec_objname))
+		return 0;
 
-		ret = apply_relocate_add(pmod->klp_info->sechdrs,
-					 pmod->core_kallsyms.strtab,
-					 pmod->klp_info->symndx, i, pmod);
-		if (ret)
-			break;
-	}
+	ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec);
+	if (ret)
+		return ret;
 
-	return ret;
+	return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
 }
 
 /*
@@ -730,6 +735,28 @@ void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
 {
 }
 
+int klp_apply_object_relocs(struct klp_patch *patch, struct klp_object *obj)
+{
+	int i, ret;
+	struct klp_modinfo *info = patch->mod->klp_info;
+
+	for (i = 1; i < info->hdr.e_shnum; i++) {
+		Elf_Shdr *sec = info->sechdrs + i;
+
+		if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
+			continue;
+
+		ret = klp_apply_section_relocs(patch->mod, info->sechdrs,
+					       info->secstrings,
+					       patch->mod->core_kallsyms.strtab,
+					       info->symndx, i, obj->name);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 /* parts of the initialization that is done only when the object is loaded */
 static int klp_init_object_loaded(struct klp_patch *patch,
 				  struct klp_object *obj)
@@ -738,18 +765,26 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 	int ret;
 
 	mutex_lock(&text_mutex);
-
 	module_disable_ro(patch->mod);
-	ret = klp_write_object_relocations(patch->mod, obj);
-	if (ret) {
-		module_enable_ro(patch->mod, true);
-		mutex_unlock(&text_mutex);
-		return ret;
+
+	if (klp_is_module(obj)) {
+		/*
+		 * Only write module-specific relocations here
+		 * (.klp.rela.{module}.*).  vmlinux-specific relocations were
+		 * written earlier during the initialization of the klp module
+		 * itself.
+		 */
+		ret = klp_apply_object_relocs(patch, obj);
+		if (ret) {
+			module_enable_ro(patch->mod, true);
+			mutex_unlock(&text_mutex);
+			return ret;
+		}
 	}
 
 	arch_klp_init_object_loaded(patch, obj);
-	module_enable_ro(patch->mod, true);
 
+	module_enable_ro(patch->mod, true);
 	mutex_unlock(&text_mutex);
 
 	klp_for_each_func(obj, func) {
diff --git a/kernel/module.c b/kernel/module.c
index 646f1e2330d2..fdd9f6970e9a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2334,11 +2334,13 @@ static int apply_relocations(struct module *mod, const struct load_info *info)
 		if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC))
 			continue;
 
-		/* Livepatch relocation sections are applied by livepatch */
 		if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH)
-			continue;
-
-		if (info->sechdrs[i].sh_type == SHT_REL)
+			err = klp_apply_section_relocs(mod, info->sechdrs,
+						       info->secstrings,
+						       info->strtab,
+						       info->index.sym, i,
+						       NULL);
+		else if (info->sechdrs[i].sh_type == SHT_REL)
 			err = apply_relocate(info->sechdrs, info->strtab,
 					     info->index.sym, i, mod);
 		else if (info->sechdrs[i].sh_type == SHT_RELA)