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Message-ID: <CAK7LNAR_=AWh1aE4iev1xtcfTAAHNOhwq3gF+h6DFzz9x39qPw@mail.gmail.com>
Date: Fri, 5 Jul 2024 01:25:19 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: HONG Yifan <elsk@...gle.com>
Cc: kernel-team@...roid.com, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] kconfig: recursive checks drop file/lineno
On Fri, Jun 28, 2024 at 8:19 AM HONG Yifan <elsk@...gle.com> wrote:
>
> This prevents segfault when getting filename and lineno in recursive
> checks.
>
> If the following snippet is found in Kconfig:
>
> [Test code 1]
>
> config FOO
> bool
> depends on BAR
> select BAR
>
> ... without BAR defined; then if one runs `make tinyconfig`, there is a
> segfault.
You do not need to mention tinyconfig because the same error happens
on any command.
... without BAR defined, there is a segfault.
>
> Kconfig:34:error: recursive dependency detected!
> Kconfig:34: symbol FOO depends on BAR
> make[4]: *** [scripts/kconfig/Makefile:85: allnoconfig] Segmentation fault
>
> This is because of the following. BAR is a fake entry created by
> sym_lookup() with prop being NULL. In the recursive check, there is a
> NULL check for prop to fall back to stack->sym->prop if stack->prop is
> NULL. However, in this case, stack->sym points to the fake BAR entry
> created by sym_lookup(), so prop is still NULL. prop was then referenced
> without additional NULL checks, causing segfault.
>
> As the previous email thread suggests, the file and lineno for select is
> also wrong:
>
> [Test code 2]
>
> config FOO
> bool
>
> config BAR
> bool
>
> config FOO
> bool "FOO"
> depends on BAR
> select BAR
>
> $ make defconfig
> *** Default configuration is based on 'x86_64_defconfig'
> Kconfig:1:error: recursive dependency detected!
> Kconfig:1: symbol FOO depends on BAR
> Kconfig:4: symbol BAR is selected by FOO
> [...]
>
> Kconfig:4 should be Kconfig:10.
>
> This patch deletes the wrong and segfault-prone filename/lineno
> inference completely. With this patch, Test code 1 yields:
>
> error: recursive dependency detected!
> symbol FOO depends on BAR
> symbol BAR is selected by FOO
>
> Link: https://lore.kernel.org/linux-kbuild/20240620211112.500465-1-elsk@google.com/
> Signed-off-by: HONG Yifan <elsk@...gle.com>
>
> --
> v3: Rebase on top of
> https://lore.kernel.org/linux-kbuild/20240626182212.3758235-1-masahiroy@kernel.org/T/#t
> & resolve merge conflicts. Fix
> scripts/kconfig/tests/err_recursive_dep/expected_stderr
> v2: Delete all filenames/lineno completely as suggested by
> masahiroy@...nel.org
> ---
> scripts/kconfig/symbol.c | 40 +++++++------------
> .../tests/err_recursive_dep/expected_stderr | 36 ++++++++---------
> 2 files changed, 33 insertions(+), 43 deletions(-)
>
> diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
> index c05d188a1857..e22c8769f44f 100644
> --- a/scripts/kconfig/symbol.c
> +++ b/scripts/kconfig/symbol.c
> @@ -1068,10 +1068,10 @@ static void sym_check_print_recursive(struct symbol *last_sym)
> {
> struct dep_stack *stack;
> struct symbol *sym, *next_sym;
> - struct menu *menu = NULL;
> struct menu *choice;
> struct property *prop;
> struct dep_stack cv_stack;
> + enum prop_type type;
>
> choice = sym_get_choice_menu(last_sym);
> if (choice) {
> @@ -1094,49 +1094,39 @@ static void sym_check_print_recursive(struct symbol *last_sym)
> if (prop == NULL)
> prop = stack->sym->prop;
As I said in the v2 review, please remove:
if (prop == NULL)
prop = stack->sym->prop;
These two lines are useless.
> - /* for choice values find the menu entry (used below) */
> - if (sym_is_choice(sym) || sym_is_choice_value(sym)) {
> - for (prop = sym->prop; prop; prop = prop->next) {
> - menu = prop->menu;
> - if (prop->menu)
> - break;
> - }
> - }
> + if (prop == NULL)
> + type = P_UNKNOWN;
> + else
> + type = prop->type;
> +
Bikeshed:
I personally prefer this:
type = prop ? prop->type : P_UNKNOWN;
> if (stack->sym == last_sym)
> - fprintf(stderr, "%s:%d:error: recursive dependency detected!\n",
> - prop->filename, prop->lineno);
> + fprintf(stderr, "error: recursive dependency detected!\n");
>
> if (sym_is_choice(next_sym)) {
> choice = list_first_entry(&next_sym->menus, struct menu, link);
>
> - fprintf(stderr, "%s:%d:\tsymbol %s is part of choice block at %s:%d\n",
> - menu->filename, menu->lineno,
> + fprintf(stderr, "\tsymbol %s is part of choice block at %s:%d\n",
> sym->name ? sym->name : "<choice>",
> choice->filename, choice->lineno);
> } else if (stack->expr == &sym->dir_dep.expr) {
> - fprintf(stderr, "%s:%d:\tsymbol %s depends on %s\n",
> - prop->filename, prop->lineno,
> + fprintf(stderr, "\tsymbol %s depends on %s\n",
> sym->name ? sym->name : "<choice>",
> next_sym->name);
> } else if (stack->expr == &sym->rev_dep.expr) {
> - fprintf(stderr, "%s:%d:\tsymbol %s is selected by %s\n",
> - prop->filename, prop->lineno,
> + fprintf(stderr, "\tsymbol %s is selected by %s\n",
> sym->name, next_sym->name);
> } else if (stack->expr == &sym->implied.expr) {
> - fprintf(stderr, "%s:%d:\tsymbol %s is implied by %s\n",
> - prop->filename, prop->lineno,
> + fprintf(stderr, "\tsymbol %s is implied by %s\n",
> sym->name, next_sym->name);
> } else if (stack->expr) {
> - fprintf(stderr, "%s:%d:\tsymbol %s %s value contains %s\n",
> - prop->filename, prop->lineno,
> + fprintf(stderr, "\tsymbol %s %s value contains %s\n",
> sym->name ? sym->name : "<choice>",
> - prop_get_type_name(prop->type),
> + prop_get_type_name(type),
> next_sym->name);
> } else {
> - fprintf(stderr, "%s:%d:\tsymbol %s %s is visible depending on %s\n",
> - prop->filename, prop->lineno,
> + fprintf(stderr, "\tsymbol %s %s is visible depending on %s\n",
> sym->name ? sym->name : "<choice>",
> - prop_get_type_name(prop->type),
> + prop_get_type_name(type),
> next_sym->name);
> }
> }
--
Best Regards
Masahiro Yamada
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