linux-kernel - [PATCH v4 06/10] s390: standardize mmap

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Date:	Wed,  4 Mar 2015 13:10:50 -0800
From:	Kees Cook <keescook@...omium.org>
To:	akpm@...ux-foundation.org
Cc:	Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...hat.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Hector Marco-Gisbert <hecmargi@....es>,
	Ismael Ripoll <iripoll@....es>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux390@...ibm.com, x86@...nel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	"David A. Long" <dave.long@...aro.org>,
	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Arun Chandran <achandran@...sta.com>,
	Yann Droneaud <ydroneaud@...eya.com>,
	Min-Hua Chen <orca.chen@...il.com>,
	Paul Burton <paul.burton@...tec.com>,
	Alex Smith <alex@...x-smith.me.uk>,
	Markos Chandras <markos.chandras@...tec.com>,
	Vineeth Vijayan <vvijayan@...sta.com>,
	Jeff Bailey <jeffbailey@...gle.com>,
	Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Borislav Petkov <bp@...e.de>,
	Jan-Simon Möller <dl9pf@....de>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mips@...ux-mips.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH v4 06/10] s390: standardize mmap_rnd() usage

In preparation for splitting out ET_DYN ASLR, this refactors the use of
mmap_rnd() to be used similarly to arm and x86, and extracts the checking
of PF_RANDOMIZE.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/s390/mm/mmap.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 179a2c20b01f..db57078075c5 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -62,20 +62,18 @@ static inline int mmap_is_legacy(void)
 
 static unsigned long mmap_rnd(void)
 {
-	if (!(current->flags & PF_RANDOMIZE))
-		return 0;
 	if (is_32bit_task())
 		return (get_random_int() & 0x7ff) << PAGE_SHIFT;
 	else
 		return (get_random_int() & mmap_rnd_mask) << PAGE_SHIFT;
 }
 
-static unsigned long mmap_base_legacy(void)
+static unsigned long mmap_base_legacy(unsigned long rnd)
 {
-	return TASK_UNMAPPED_BASE + mmap_rnd();
+	return TASK_UNMAPPED_BASE + rnd;
 }
 
-static inline unsigned long mmap_base(void)
+static inline unsigned long mmap_base(unsigned long rnd)
 {
 	unsigned long gap = rlimit(RLIMIT_STACK);
 
@@ -84,7 +82,7 @@ static inline unsigned long mmap_base(void)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 	gap &= PAGE_MASK;
-	return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
+	return STACK_TOP - stack_maxrandom_size() - rnd - gap;
 }
 
 unsigned long
@@ -187,7 +185,11 @@ unsigned long randomize_et_dyn(void)
 	if (!is_32bit_task())
 		/* Align to 4GB */
 		base &= ~((1UL << 32) - 1);
-	return base + mmap_rnd();
+
+	if (current->flags & PF_RANDOMIZE)
+		base += mmap_rnd();
+
+	return base;
 }
 
 #ifndef CONFIG_64BIT
@@ -198,15 +200,20 @@ unsigned long randomize_et_dyn(void)
  */
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
+	unsigned long random_factor = 0UL;
+
+	if (current->flags & PF_RANDOMIZE)
+		random_factor = mmap_rnd();
+
 	/*
 	 * Fall back to the standard layout if the personality
 	 * bit is set, or if the expected stack growth is unlimited:
 	 */
 	if (mmap_is_legacy()) {
-		mm->mmap_base = mmap_base_legacy();
+		mm->mmap_base = mmap_base_legacy(random_factor);
 		mm->get_unmapped_area = arch_get_unmapped_area;
 	} else {
-		mm->mmap_base = mmap_base();
+		mm->mmap_base = mmap_base(random_factor);
 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 	}
 }
@@ -273,15 +280,20 @@ s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
  */
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
+	unsigned long random_factor = 0UL;
+
+	if (current->flags & PF_RANDOMIZE)
+		random_factor = mmap_rnd();
+
 	/*
 	 * Fall back to the standard layout if the personality
 	 * bit is set, or if the expected stack growth is unlimited:
 	 */
 	if (mmap_is_legacy()) {
-		mm->mmap_base = mmap_base_legacy();
+		mm->mmap_base = mmap_base_legacy(random_factor);
 		mm->get_unmapped_area = s390_get_unmapped_area;
 	} else {
-		mm->mmap_base = mmap_base();
+		mm->mmap_base = mmap_base(random_factor);
 		mm->get_unmapped_area = s390_get_unmapped_area_topdown;
 	}
 }
-- 
1.9.1

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