From 389eb3f5f4abbdb9810458ac9b87427336ba5b91 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Thu, 3 Oct 2019 16:58:22 +0900 Subject: [PATCH] modpost: fix broken sym->namespace for external module builds Currently, external module builds produce tons of false-positives: WARNING: module uses symbol from namespace , but does not import it. Here, the part shows a random string. When you build external modules, the symbol info of vmlinux and in-kernel modules are read from $(objtree)/Module.symvers, but read_dump() is buggy in multiple ways: [1] When the modpost is run for vmlinux and in-kernel modules, sym_extract_namespace() allocates memory for the namespace. On the other hand, read_dump() does not, then sym->namespace will point to somewhere in the line buffer of get_next_line(). The data in the buffer will be replaced soon, and sym->namespace will end up with pointing to unrelated data. As a result, check_exports() will show random strings in the warning messages. [2] When there is no namespace, sym_extract_namespace() returns NULL. On the other hand, read_dump() sets namespace to an empty string "". (but, it will be later replaced with unrelated data due to bug [1].) The check_exports() shows a warning unless exp->namespace is NULL, so every symbol read from read_dump() emits the warning, which is mostly false positive. To address [1], sym_add_exported() calls strdup() for s->namespace. The namespace from sym_extract_namespace() must be freed to avoid memory leak. For [2], I changed the if-conditional in check_exports(). This commit also fixes sym_add_exported() to set s->namespace correctly when the symbol is preloaded. Reviewed-by: Matthias Maennich Signed-off-by: Masahiro Yamada Signed-off-by: Jessica Yu --- scripts/mod/modpost.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index c4b536ac1327..4d2cdb4d71e3 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -166,7 +166,7 @@ struct symbol { struct module *module; unsigned int crc; int crc_valid; - const char *namespace; + char *namespace; unsigned int weak:1; unsigned int vmlinux:1; /* 1 if symbol is defined in vmlinux */ unsigned int kernel:1; /* 1 if symbol is from kernel @@ -348,7 +348,7 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec) return export_unknown; } -static const char *sym_extract_namespace(const char **symname) +static char *sym_extract_namespace(const char **symname) { char *namespace = NULL; char *ns_separator; @@ -373,7 +373,6 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace, if (!s) { s = new_symbol(name, mod, export); - s->namespace = namespace; } else { if (!s->preloaded) { warn("%s: '%s' exported twice. Previous export was in %s%s\n", @@ -384,6 +383,8 @@ static struct symbol *sym_add_exported(const char *name, const char *namespace, s->module = mod; } } + free(s->namespace); + s->namespace = namespace ? strdup(namespace) : NULL; s->preloaded = 0; s->vmlinux = is_vmlinux(mod->name); s->kernel = 0; @@ -670,7 +671,8 @@ static void handle_modversions(struct module *mod, struct elf_info *info, unsigned int crc; enum export export; bool is_crc = false; - const char *name, *namespace; + const char *name; + char *namespace; if ((!is_vmlinux(mod->name) || mod->is_dot_o) && strstarts(symname, "__ksymtab")) @@ -745,6 +747,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info, name = symname + strlen("__ksymtab_"); namespace = sym_extract_namespace(&name); sym_add_exported(name, namespace, mod, export); + free(namespace); } if (strcmp(symname, "init_module") == 0) mod->has_init = 1; @@ -2193,7 +2196,7 @@ static int check_exports(struct module *mod) else basename = mod->name; - if (exp->namespace) { + if (exp->namespace && exp->namespace[0]) { add_namespace(&mod->required_namespaces, exp->namespace);