Commit 08126db5 authored by Aaron Tomlin's avatar Aaron Tomlin Committed by Luis Chamberlain
Browse files

module: kallsyms: Fix suspicious rcu usage 



No functional change.

The purpose of this patch is to address the various Sparse warnings
due to the incorrect dereference/or access of an __rcu pointer.

Signed-off-by: default avatarAaron Tomlin <atomlin@redhat.com>
Signed-off-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
parent 91fb02f3

kernel/module/kallsyms.c

+22 −12
Original line number Diff line number Diff line
@@ -171,14 +171,17 @@ void add_kallsyms(struct module *mod, const struct load_info *info) 
	Elf_Shdr *symsec = &info->sechdrs[info->index.sym];



	/* Set up to point into init section. */

	mod->kallsyms = mod->init_layout.base + info->mod_kallsyms_init_off;

	mod->kallsyms = (void __rcu *)mod->init_layout.base +

		info->mod_kallsyms_init_off;



	preempt_disable();

	/* The following is safe since this pointer cannot change */

	mod->kallsyms->symtab = (void *)symsec->sh_addr;

	mod->kallsyms->num_symtab = symsec->sh_size / sizeof(Elf_Sym);

	rcu_dereference_sched(mod->kallsyms)->symtab = (void *)symsec->sh_addr;

	rcu_dereference_sched(mod->kallsyms)->num_symtab = symsec->sh_size / sizeof(Elf_Sym);

	/* Make sure we get permanent strtab: don't use info->strtab. */

	mod->kallsyms->strtab = (void *)info->sechdrs[info->index.str].sh_addr;

	mod->kallsyms->typetab = mod->init_layout.base + info->init_typeoffs;

	rcu_dereference_sched(mod->kallsyms)->strtab =

		(void *)info->sechdrs[info->index.str].sh_addr;

	rcu_dereference_sched(mod->kallsyms)->typetab = mod->init_layout.base + info->init_typeoffs;



	/*

	 * Now populate the cut down core kallsyms for after init
@@ -187,20 +190,22 @@ void add_kallsyms(struct module *mod, const struct load_info *info) 
	mod->core_kallsyms.symtab = dst = mod->core_layout.base + info->symoffs;

	mod->core_kallsyms.strtab = s = mod->core_layout.base + info->stroffs;

	mod->core_kallsyms.typetab = mod->core_layout.base + info->core_typeoffs;

	src = mod->kallsyms->symtab;

	for (ndst = i = 0; i < mod->kallsyms->num_symtab; i++) {

		mod->kallsyms->typetab[i] = elf_type(src + i, info);

	src = rcu_dereference_sched(mod->kallsyms)->symtab;

	for (ndst = i = 0; i < rcu_dereference_sched(mod->kallsyms)->num_symtab; i++) {

		rcu_dereference_sched(mod->kallsyms)->typetab[i] = elf_type(src + i, info);

		if (i == 0 || is_livepatch_module(mod) ||

		    is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum,

				   info->index.pcpu)) {

			mod->core_kallsyms.typetab[ndst] =

			    mod->kallsyms->typetab[i];

			    rcu_dereference_sched(mod->kallsyms)->typetab[i];

			dst[ndst] = src[i];

			dst[ndst++].st_name = s - mod->core_kallsyms.strtab;

			s += strscpy(s, &mod->kallsyms->strtab[src[i].st_name],

			s += strscpy(s,

				     &rcu_dereference_sched(mod->kallsyms)->strtab[src[i].st_name],

				     KSYM_NAME_LEN) + 1;

		}

	}

	preempt_enable();

	mod->core_kallsyms.num_symtab = ndst;

}
@@ -478,11 +483,16 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *, 


	mutex_lock(&module_mutex);

	list_for_each_entry(mod, &modules, list) {

		/* We hold module_mutex: no need for rcu_dereference_sched */

		struct mod_kallsyms *kallsyms = mod->kallsyms;

		struct mod_kallsyms *kallsyms;



		if (mod->state == MODULE_STATE_UNFORMED)

			continue;



		/* Use rcu_dereference_sched() to remain compliant with the sparse tool */

		preempt_disable();

		kallsyms = rcu_dereference_sched(mod->kallsyms);

		preempt_enable();



		for (i = 0; i < kallsyms->num_symtab; i++) {

			const Elf_Sym *sym = &kallsyms->symtab[i];