[PATCH][SRU Artful] arm64: fix CONFIG_DEBUG_WX address reporting

[dann frazier]

From: Mark Rutland <mark.rutland at arm.com>

BugLink: https://bugs.launchpad.net/bugs/1765850

In ptdump_check_wx(), we pass walk_pgd() a start address of 0 (rather
than VA_START) for the init_mm. This means that any reported W&X
addresses are offset by VA_START, which is clearly wrong and can make
them appear like userspace addresses.

Fix this by telling the ptdump code that we're walking init_mm starting
at VA_START. We don't need to update the addr_markers, since these are
still valid bounds regardless.

Cc: <stable at vger.kernel.org>
Fixes: 1404d6f13e47 ("arm64: dump: Add checking for writable and exectuable pages")
Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Laura Abbott <labbott at redhat.com>
Reported-by: Timur Tabi <timur at codeaurora.org>
Signed-off-by: Will Deacon <will.deacon at arm.com>
(cherry picked from commit 1d08a044cf12aee37dfd54837558e3295287b343)
Signed-off-by: dann frazier <dann.frazier at canonical.com>
---
 arch/arm64/mm/dump.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index ca74a2aace42..7b60d62ac593 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -389,7 +389,7 @@ void ptdump_check_wx(void)
 		.check_wx = true,
 	};
 
-	walk_pgd(&st, &init_mm, 0);
+	walk_pgd(&st, &init_mm, VA_START);
 	note_page(&st, 0, 0, 0);
 	if (st.wx_pages || st.uxn_pages)
 		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
-- 
2.17.0