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[82.17.115.212]) by smtp.gmail.com with ESMTPSA id b3-20020adfd1c3000000b00205820686dasm16295wrd.5.2022.03.22.07.04.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Mar 2022 07:04:13 -0700 (PDT) From: Aaron Tomlin To: mcgrof@kernel.org, christophe.leroy@csgroup.eu Cc: cl@linux.com, mbenes@suse.cz, akpm@linux-foundation.org, jeyu@kernel.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, void@manifault.com, atomlin@atomlin.com, allen.lkml@gmail.com, joe@perches.com, msuchanek@suse.de, oleksandr@natalenko.name, jason.wessel@windriver.com, pmladek@suse.com, daniel.thompson@linaro.org, hch@infradead.org Subject: [PATCH v12 10/14] module: kallsyms: Fix suspicious rcu usage Date: Tue, 22 Mar 2022 14:03:40 +0000 Message-Id: <20220322140344.556474-11-atomlin@redhat.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220322140344.556474-1-atomlin@redhat.com> References: <20220322140344.556474-1-atomlin@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: Aaron Tomlin --- kernel/module/kallsyms.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c index 1b0780e20aab..a3da0686a2a6 100644 --- a/kernel/module/kallsyms.c +++ b/kernel/module/kallsyms.c @@ -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]; -- 2.34.1