[PATCH 4.19 088/118] ARM: 8806/1: kprobes: Fix false positive with FORTIFY_SOURCE

Greg Kroah-Hartman
2018-12-11T15:57:33Z

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