linux-kernel - [PATCH] x86, UML: fix integer overflow in ELF_ET_DYN

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Date:	Tue, 24 Mar 2015 18:31:24 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	user-mode-linux-devel@...ts.sourceforge.net,
	user-mode-linux-user@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Cc:	Kees Cook <keescook@...omium.org>,
	Yury Gribov <y.gribov@...sung.com>,
	Andrey Ryabinin <a.ryabinin@...sung.com>
Subject: [PATCH] x86, UML: fix integer overflow in ELF_ET_DYN_BASE

Almost all arches define ELF_ET_DYN_BASE as 2/3 of TASK_SIZE.
Though it seems that some architectures do this in a wrong way.
The problem is that 2*TASK_SIZE may overflow 32-bits so
the real ELF_ET_DYN_BASE becomes wrong.
Fix this overflow by dividing TASK_SIZE prior to multiplying:
	(TASK_SIZE / 3 * 2)

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
---
 arch/x86/um/asm/elf.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/um/asm/elf.h b/arch/x86/um/asm/elf.h
index 25a1022..0a656b7 100644
--- a/arch/x86/um/asm/elf.h
+++ b/arch/x86/um/asm/elf.h
@@ -210,7 +210,7 @@ extern int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu);
 
 #define ELF_EXEC_PAGESIZE 4096
 
-#define ELF_ET_DYN_BASE (2 * TASK_SIZE / 3)
+#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2)
 
 extern long elf_aux_hwcap;
 #define ELF_HWCAP (elf_aux_hwcap)
-- 
2.3.3

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