linux-kernel - [PATCH v2 2/2] x86/elf: remove the unnecessary ADDR_NO_RANDOMIZE checks in stack_maxrandom_size() and randomize_stack

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Date:   Tue, 15 Aug 2017 17:40:11 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...e.de>,
        Dmitry Safonov <dsafonov@...tuozzo.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        stable@...r.kernel.org
Subject: [PATCH v2 2/2] x86/elf: remove the unnecessary ADDR_NO_RANDOMIZE
 checks in stack_maxrandom_size() and randomize_stack_top()

PF_RANDOMIZE is set by load_elf_binary() only if ADDR_NO_RANDOMIZE is not
set, no need to re-check after that.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Dmitry Safonov <dsafonov@...tuozzo.com>
---
 arch/x86/mm/mmap.c | 3 +--
 fs/binfmt_elf.c    | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index c94df12..a88cfbf 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -50,8 +50,7 @@ unsigned long tasksize_64bit(void)
 static unsigned long stack_maxrandom_size(unsigned long task_size)
 {
 	unsigned long max = 0;
-	if ((current->flags & PF_RANDOMIZE) &&
-		!(current->personality & ADDR_NO_RANDOMIZE)) {
+	if (current->flags & PF_RANDOMIZE) {
 		max = (-1UL) & __STACK_RND_MASK(task_size == tasksize_32bit());
 		max <<= PAGE_SHIFT;
 	}
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 879ff9c..6466153 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -664,8 +664,7 @@ static unsigned long randomize_stack_top(unsigned long stack_top)
 {
 	unsigned long random_variable = 0;
 
-	if ((current->flags & PF_RANDOMIZE) &&
-		!(current->personality & ADDR_NO_RANDOMIZE)) {
+	if (current->flags & PF_RANDOMIZE) {
 		random_variable = get_random_long();
 		random_variable &= STACK_RND_MASK;
 		random_variable <<= PAGE_SHIFT;
-- 
2.5.0