linux-kernel - [PATCH 4.14 46/67] ARM: 8806/1: kprobes: Fix false positive with FORTIFY

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Date:   Tue, 11 Dec 2018 16:41:46 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, William Cohen <wcohen@...hat.com>,
        Laura Abbott <labbott@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Russell King <rmk+kernel@...linux.org.uk>
Subject: [PATCH 4.14 46/67] ARM: 8806/1: kprobes: Fix false positive with FORTIFY_SOURCE

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@...omium.org>

commit e46daee53bb50bde38805f1823a182979724c229 upstream.

The arm compiler internally interprets an inline assembly label
as an unsigned long value, not a pointer. As a result, under
CONFIG_FORTIFY_SOURCE, the address of a label has a size of 4 bytes,
which was tripping the runtime checks. Instead, we can just cast the label
(as done with the size calculations earlier).

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1639397

Reported-by: William Cohen <wcohen@...hat.com>
Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
Cc: stable@...r.kernel.org
Acked-by: Laura Abbott <labbott@...hat.com>
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
Tested-by: William Cohen <wcohen@...hat.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/probes/kprobes/opt-arm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm/probes/kprobes/opt-arm.c
+++ b/arch/arm/probes/kprobes/opt-arm.c
@@ -247,7 +247,7 @@ int arch_prepare_optimized_kprobe(struct
 	}
 
 	/* Copy arch-dep-instance from template. */
-	memcpy(code, &optprobe_template_entry,
+	memcpy(code, (unsigned char *)optprobe_template_entry,
 			TMPL_END_IDX * sizeof(kprobe_opcode_t));
 
 	/* Adjust buffer according to instruction. */