linux-hardening - [PATCH 3/3] gcc-plugins/stackleak: Ignore .noinstr.text and .entry.text

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Date:   Sun,  6 Feb 2022 09:45:08 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Alexander Popov <alex.popov@...ux.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Masahiro Yamada <masahiroy@...nel.org>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH 3/3] gcc-plugins/stackleak: Ignore .noinstr.text and .entry.text

The .noinstr.text section functions may not have "current()" sanely
available. Similarly true for .entry.text, though such a check is
currently redundant. Add a check for both. In an x86_64 defconfig build,
the following functions no longer receive stackleak instrumentation:

	__do_fast_syscall_32()
	do_int80_syscall_32()
	do_machine_check()
	do_syscall_64()
	exc_general_protection()
	fixup_bad_iret()

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Cc: Alexander Popov <alex.popov@...ux.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 scripts/gcc-plugins/stackleak_plugin.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
index 623bcad6d0c7..c8dc7fe4f959 100644
--- a/scripts/gcc-plugins/stackleak_plugin.c
+++ b/scripts/gcc-plugins/stackleak_plugin.c
@@ -463,6 +463,10 @@ static bool stackleak_gate(void)
 			return false;
 		if (STRING_EQUAL(section, ".meminit.text"))
 			return false;
+		if (STRING_EQUAL(section, ".noinstr.text"))
+			return false;
+		if (STRING_EQUAL(section, ".entry.text"))
+			return false;
 	}
 
 	return track_frame_size >= 0;
-- 
2.30.2