From d1fd836dcf00d2028c700c7e44d2c23404062c90 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 14 Apr 2015 15:48:07 -0700 Subject: mm: split ET_DYN ASLR from mmap ASLR This fixes the "offset2lib" weakness in ASLR for arm, arm64, mips, powerpc, and x86. The problem is that if there is a leak of ASLR from the executable (ET_DYN), it means a leak of shared library offset as well (mmap), and vice versa. Further details and a PoC of this attack is available here: http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html With this patch, a PIE linked executable (ET_DYN) has its own ASLR region: $ ./show_mmaps_pie 54859ccd6000-54859ccd7000 r-xp ... /tmp/show_mmaps_pie 54859ced6000-54859ced7000 r--p ... /tmp/show_mmaps_pie 54859ced7000-54859ced8000 rw-p ... /tmp/show_mmaps_pie 7f75be764000-7f75be91f000 r-xp ... /lib/x86_64-linux-gnu/libc.so.6 7f75be91f000-7f75beb1f000 ---p ... /lib/x86_64-linux-gnu/libc.so.6 7f75beb1f000-7f75beb23000 r--p ... /lib/x86_64-linux-gnu/libc.so.6 7f75beb23000-7f75beb25000 rw-p ... /lib/x86_64-linux-gnu/libc.so.6 7f75beb25000-7f75beb2a000 rw-p ... 7f75beb2a000-7f75beb4d000 r-xp ... /lib64/ld-linux-x86-64.so.2 7f75bed45000-7f75bed46000 rw-p ... 7f75bed46000-7f75bed47000 r-xp ... 7f75bed47000-7f75bed4c000 rw-p ... 7f75bed4c000-7f75bed4d000 r--p ... /lib64/ld-linux-x86-64.so.2 7f75bed4d000-7f75bed4e000 rw-p ... /lib64/ld-linux-x86-64.so.2 7f75bed4e000-7f75bed4f000 rw-p ... 7fffb3741000-7fffb3762000 rw-p ... [stack] 7fffb377b000-7fffb377d000 r--p ... [vvar] 7fffb377d000-7fffb377f000 r-xp ... [vdso] The change is to add a call the newly created arch_mmap_rnd() into the ELF loader for handling ET_DYN ASLR in a separate region from mmap ASLR, as was already done on s390. Removes CONFIG_BINFMT_ELF_RANDOMIZE_PIE, which is no longer needed. Signed-off-by: Kees Cook Reported-by: Hector Marco-Gisbert Cc: Russell King Reviewed-by: Ingo Molnar Cc: Catalin Marinas Cc: Will Deacon Cc: Ralf Baechle Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Alexander Viro Cc: Oleg Nesterov Cc: Andy Lutomirski Cc: "David A. Long" Cc: Andrey Ryabinin Cc: Arun Chandran Cc: Yann Droneaud Cc: Min-Hua Chen Cc: Paul Burton Cc: Alex Smith Cc: Markos Chandras Cc: Vineeth Vijayan Cc: Jeff Bailey Cc: Michael Holzheu Cc: Ben Hutchings Cc: Behan Webster Cc: Ismael Ripoll Cc: Jan-Simon Mller Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/s390/include/asm/elf.h | 5 ++--- arch/s390/mm/mmap.c | 8 -------- 2 files changed, 2 insertions(+), 11 deletions(-) (limited to 'arch/s390') diff --git a/arch/s390/include/asm/elf.h b/arch/s390/include/asm/elf.h index f8db4781a4c2..ff662155b2c4 100644 --- a/arch/s390/include/asm/elf.h +++ b/arch/s390/include/asm/elf.h @@ -163,10 +163,9 @@ extern unsigned int vdso_enabled; the loader. We need to make sure that it is out of the way of the program that it will "exec", and that there is sufficient room for the brk. 64-bit tasks are aligned to 4GB. */ -extern unsigned long randomize_et_dyn(void); -#define ELF_ET_DYN_BASE (randomize_et_dyn() + (is_32bit_task() ? \ +#define ELF_ET_DYN_BASE (is_32bit_task() ? \ (STACK_TOP / 3 * 2) : \ - (STACK_TOP / 3 * 2) & ~((1UL << 32) - 1))) + (STACK_TOP / 3 * 2) & ~((1UL << 32) - 1)) /* This yields a mask that user programs can use to figure out what instruction set this CPU supports. */ diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c index 8c11536f972d..bb3367c5cb0b 100644 --- a/arch/s390/mm/mmap.c +++ b/arch/s390/mm/mmap.c @@ -177,14 +177,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, return addr; } -unsigned long randomize_et_dyn(void) -{ - if (current->flags & PF_RANDOMIZE) - return arch_mmap_rnd(); - - return 0UL; -} - #ifndef CONFIG_64BIT /* -- cgit v1.2.3