diff mbox series

[3/5] modpost: simplify mod->name allocation

Message ID 20220523164626.858340-3-masahiroy@kernel.org (mailing list archive)
State New
Headers show
Series [1/5] modpost: fix undefined behavior of is_arm_mapping_symbol() | expand

Commit Message

Masahiro Yamada May 23, 2022, 4:46 p.m. UTC
mod->name is set to the ELF filename with the suffix ".o" stripped.

The current code calls strdup() and free() to manipulate the string,
but a simpler approach is to pass new_module() with the name length
subtracted by 2.

Also, check if the passed filename ends with ".o" before stripping it.

The current code blindly chops the suffix

    tmp[strlen(tmp) - 2] = '\0'

but it will cause buffer under-run if strlen(tmp) < 2;

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/mod/modpost.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

Comments

Nick Desaulniers May 24, 2022, 8:47 p.m. UTC | #1
On Mon, May 23, 2022 at 9:48 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> mod->name is set to the ELF filename with the suffix ".o" stripped.
>
> The current code calls strdup() and free() to manipulate the string,
> but a simpler approach is to pass new_module() with the name length
> subtracted by 2.
>
> Also, check if the passed filename ends with ".o" before stripping it.
>
> The current code blindly chops the suffix
>
>     tmp[strlen(tmp) - 2] = '\0'
>
> but it will cause buffer under-run if strlen(tmp) < 2;
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>
>  scripts/mod/modpost.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 843c64eebe8b..77c315dea1a3 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -172,11 +172,11 @@ static struct module *find_module(const char *modname)
>         return NULL;
>  }
>
> -static struct module *new_module(const char *modname)
> +static struct module *new_module(const char *name, size_t namelen)
>  {
>         struct module *mod;
>
> -       mod = NOFAIL(malloc(sizeof(*mod) + strlen(modname) + 1));
> +       mod = NOFAIL(malloc(sizeof(*mod) + namelen + 1));
>         memset(mod, 0, sizeof(*mod));
>
>         INIT_LIST_HEAD(&mod->exported_symbols);
> @@ -184,8 +184,9 @@ static struct module *new_module(const char *modname)
>         INIT_LIST_HEAD(&mod->missing_namespaces);
>         INIT_LIST_HEAD(&mod->imported_namespaces);
>
> -       strcpy(mod->name, modname);
> -       mod->is_vmlinux = (strcmp(modname, "vmlinux") == 0);
> +       memcpy(mod->name, name, namelen);
> +       mod->name[namelen] = '\0';
> +       mod->is_vmlinux = (strcmp(mod->name, "vmlinux") == 0);
>
>         /*
>          * Set mod->is_gpl_compatible to true by default. If MODULE_LICENSE()
> @@ -2022,16 +2023,14 @@ static void read_symbols(const char *modname)
>         if (!parse_elf(&info, modname))
>                 return;
>
> -       {
> -               char *tmp;
> -
> -               /* strip trailing .o */
> -               tmp = NOFAIL(strdup(modname));
> -               tmp[strlen(tmp) - 2] = '\0';
> -               mod = new_module(tmp);
> -               free(tmp);
> +       if (!strends(modname, ".o")) {
> +               error("%s: filename must be suffixed with .o\n", modname);
> +               return;
>         }
>
> +       /* strip trailing .o */
> +       mod = new_module(modname, strlen(modname) - strlen(".o"));
> +
>         if (!mod->is_vmlinux) {
>                 license = get_modinfo(&info, "license");
>                 if (!license)
> @@ -2493,7 +2492,7 @@ static void read_dump(const char *fname)
>
>                 mod = find_module(modname);
>                 if (!mod) {
> -                       mod = new_module(modname);
> +                       mod = new_module(modname, strlen(modname));
>                         mod->from_dump = true;
>                 }
>                 s = sym_add_exported(symname, mod, gpl_only);
> --
> 2.32.0
>
diff mbox series

Patch

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 843c64eebe8b..77c315dea1a3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -172,11 +172,11 @@  static struct module *find_module(const char *modname)
 	return NULL;
 }
 
-static struct module *new_module(const char *modname)
+static struct module *new_module(const char *name, size_t namelen)
 {
 	struct module *mod;
 
-	mod = NOFAIL(malloc(sizeof(*mod) + strlen(modname) + 1));
+	mod = NOFAIL(malloc(sizeof(*mod) + namelen + 1));
 	memset(mod, 0, sizeof(*mod));
 
 	INIT_LIST_HEAD(&mod->exported_symbols);
@@ -184,8 +184,9 @@  static struct module *new_module(const char *modname)
 	INIT_LIST_HEAD(&mod->missing_namespaces);
 	INIT_LIST_HEAD(&mod->imported_namespaces);
 
-	strcpy(mod->name, modname);
-	mod->is_vmlinux = (strcmp(modname, "vmlinux") == 0);
+	memcpy(mod->name, name, namelen);
+	mod->name[namelen] = '\0';
+	mod->is_vmlinux = (strcmp(mod->name, "vmlinux") == 0);
 
 	/*
 	 * Set mod->is_gpl_compatible to true by default. If MODULE_LICENSE()
@@ -2022,16 +2023,14 @@  static void read_symbols(const char *modname)
 	if (!parse_elf(&info, modname))
 		return;
 
-	{
-		char *tmp;
-
-		/* strip trailing .o */
-		tmp = NOFAIL(strdup(modname));
-		tmp[strlen(tmp) - 2] = '\0';
-		mod = new_module(tmp);
-		free(tmp);
+	if (!strends(modname, ".o")) {
+		error("%s: filename must be suffixed with .o\n", modname);
+		return;
 	}
 
+	/* strip trailing .o */
+	mod = new_module(modname, strlen(modname) - strlen(".o"));
+
 	if (!mod->is_vmlinux) {
 		license = get_modinfo(&info, "license");
 		if (!license)
@@ -2493,7 +2492,7 @@  static void read_dump(const char *fname)
 
 		mod = find_module(modname);
 		if (!mod) {
-			mod = new_module(modname);
+			mod = new_module(modname, strlen(modname));
 			mod->from_dump = true;
 		}
 		s = sym_add_exported(symname, mod, gpl_only);