3.19.8-ckt21 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Kees Cook <keescook@xxxxxxxxxxxx> commit fbbc400f3924ce095b466c776dc294727ec0a202 upstream. To address the "offset2lib" ASLR weakness[1], this separates ET_DYN ASLR from mmap ASLR, as already done on s390. The architectures that are already randomizing mmap (arm, arm64, mips, powerpc, s390, and x86), have their various forms of arch_mmap_rnd() made available via the new CONFIG_ARCH_HAS_ELF_RANDOMIZE. For these architectures, arch_randomize_brk() is collapsed as well. This is an alternative to the solutions in: https://lkml.org/lkml/2015/2/23/442 I've been able to test x86 and arm, and the buildbot (so far) seems happy with building the rest. [1] http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html This patch (of 10): In preparation for splitting out ET_DYN ASLR, this moves the ASLR calculations for mmap on ARM into a separate routine, similar to x86. This also removes the redundant check of personality (PF_RANDOMIZE is already set before calling arch_pick_mmap_layout). Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Hector Marco-Gisbert <hecmargi@xxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: "David A. Long" <dave.long@xxxxxxxxxx> Cc: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> Cc: Arun Chandran <achandran@xxxxxxxxxx> Cc: Yann Droneaud <ydroneaud@xxxxxxxxxx> Cc: Min-Hua Chen <orca.chen@xxxxxxxxx> Cc: Paul Burton <paul.burton@xxxxxxxxxx> Cc: Alex Smith <alex@xxxxxxxxxxxxxxxx> Cc: Markos Chandras <markos.chandras@xxxxxxxxxx> Cc: Vineeth Vijayan <vvijayan@xxxxxxxxxx> Cc: Jeff Bailey <jeffbailey@xxxxxxxxxx> Cc: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx> Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Cc: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx> Cc: Ismael Ripoll <iripoll@xxxxxx> Cc: Jan-Simon Mller <dl9pf@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- arch/arm/mm/mmap.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c index 5e85ed3..15a8160 100644 --- a/arch/arm/mm/mmap.c +++ b/arch/arm/mm/mmap.c @@ -169,14 +169,22 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, return addr; } +static unsigned long mmap_rnd(void) +{ + unsigned long rnd; + + /* 8 bits of randomness in 20 address space bits */ + rnd = (unsigned long)get_random_int() % (1 << 8); + + return rnd << PAGE_SHIFT; +} + void arch_pick_mmap_layout(struct mm_struct *mm) { unsigned long random_factor = 0UL; - /* 8 bits of randomness in 20 address space bits */ - if ((current->flags & PF_RANDOMIZE) && - !(current->personality & ADDR_NO_RANDOMIZE)) - random_factor = (get_random_int() % (1 << 8)) << PAGE_SHIFT; + if (current->flags & PF_RANDOMIZE) + random_factor = mmap_rnd(); if (mmap_is_legacy()) { mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html