linux-kernel - [PATCH] /proc/modules: honor kptr_restrict even without CONFIG

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Message-ID: <20220605224347.481e2fb4@mocarz>
Date:   Sun, 5 Jun 2022 22:43:47 +0200
From:   Aleksander Mazur <deweloper@...pl>
To:     Arnd Bergmann <arnd@...db.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Aleksander Mazur <deweloper@...pl>, linux-kernel@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH] /proc/modules: honor kptr_restrict even without
 CONFIG_KALLSYMS

Commit e4a8ca3baa55 fixed building without CONFIG_KALLSYMS by providing
dummy kallsyms_show_value(). Unfortunately -- due to hard-coded "false"
being returned -- access to addresses in /proc/modules became permanently
disabled.

My proposal is to change this unconditional "false" to !kptr_restrict.
This re-enables addresses in /proc/modules even without CONFIG_KALLSYSMS
unless restricted by means of sysctl (kernel.kptr_restrict).

Fixes: e4a8ca3baa55 ("/proc/module: fix building without kallsyms")
Signed-off-by: Aleksander Mazur <deweloper@...pl>
---
 include/linux/kallsyms.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index ad39636e0c3f..cf64f9709f46 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -160,7 +160,7 @@ static inline int lookup_symbol_attrs(unsigned long addr, unsigned long *size, u
 
 static inline bool kallsyms_show_value(const struct cred *cred)
 {
-	return false;
+	return !kptr_restrict;
 }
 
 static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
-- 
2.36.1