linux-kernel - [PATCH v1 09/10] lkdtm: Fix lkdtm_EXEC

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Date:   Mon, 11 Oct 2021 17:25:36 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>, Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-ia64@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v1 09/10] lkdtm: Fix lkdtm_EXEC_RODATA()

Behind a location, lkdtm_EXEC_RODATA() executes a real function,
not a copy of do_nothing().

So do it directly instead of using execute_location().

And fix displayed addresses by dereferencing the function descriptors.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 drivers/misc/lkdtm/perms.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 442d60ed25ef..da16564e1ecd 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
 
 void lkdtm_EXEC_RODATA(void)
 {
-	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+	pr_info("attempting ok execution at %px\n",
+		dereference_symbol_descriptor(do_nothing));
+	do_nothing();
+
+	pr_info("attempting bad execution at %px\n",
+		dereference_symbol_descriptor(lkdtm_rodata_do_nothing));
+	lkdtm_rodata_do_nothing();
+	pr_err("FAIL: func returned\n");
 }
 
 void lkdtm_EXEC_USERSPACE(void)
-- 
2.31.1