linux-kernel - [PATCH v3 4/7] arm64: Use simpler API for random address requests

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Message-Id: <20160803233913.32511-5-jason@lakedaemon.net>
Date:	Wed,  3 Aug 2016 23:39:10 +0000
From:	Jason Cooper <jason@...edaemon.net>
To:	Kees Cook <keescook@...omium.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Roberts, William C" <william.c.roberts@...el.com>,
	Yann Droneaud <ydroneaud@...eya.com>
Cc:	"Linux-MM" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"kernel-hardening" <kernel-hardening@...ts.openwall.com>,
	"Russell King - ARM Linux" <linux@....linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Theodore Ts'o" <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
	gregkh@...uxfoundation.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Ralf Baechle <ralf@...ux-mips.org>, benh@...nel.crashing.org,
	paulus@...ba.org, "David S. Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	viro@...iv.linux.org.uk, Nick Kralevich <nnk@...gle.com>,
	Jeffrey Vander Stoep <jeffv@...gle.com>,
	Daniel Cashman <dcashman@...roid.com>,
	Jason Cooper <jason@...edaemon.net>
Subject: [PATCH v3 4/7] arm64: Use simpler API for random address requests

Currently, all callers to randomize_range() set the length to 0 and
calculate end by adding a constant to the start address.  We can
simplify the API to remove a bunch of needless checks and variables.

Use the new randomize_addr(start, range) call to set the requested
address.

Signed-off-by: Jason Cooper <jason@...edaemon.net>
Acked-by: Will Deacon <will.deacon@....com>
---
Changes from v2:
 - s/randomize_addr/randomize_page/ (Kees Cook)

 arch/arm64/kernel/process.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6cd2612236dc..6ac2950ffb78 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -374,12 +374,8 @@ unsigned long arch_align_stack(unsigned long sp)
 
 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {
-	unsigned long range_end = mm->brk;
-
 	if (is_compat_task())
-		range_end += 0x02000000;
+		return randomize_page(mm->brk, 0x02000000);
 	else
-		range_end += 0x40000000;
-
-	return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
+		return randomize_page(mm->brk, 0x40000000);
 }
-- 
2.9.2