[PATCH v4 05/10] powerpc: standardize mmap_rnd() usage
From: Kees Cook <hidden>
Date: 2015-03-04 21:10:49
Also in:
linux-arm-kernel, linux-fsdevel, linux-mips, lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
In preparation for splitting out ET_DYN ASLR, this refactors the use of mmap_rnd() to be used similarly to arm and x86. Signed-off-by: Kees Cook <redacted> Acked-by: Michael Ellerman <mpe@ellerman.id.au> --- Can mmap ASLR be safely enabled in the legacy mmap case here? Other archs use "mm->mmap_base = TASK_UNMAPPED_BASE + random_factor". --- arch/powerpc/mm/mmap.c | 26 +++++++++++++++----------- 1 file changed, 15 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index cb8bdbe4972f..1ad2299d795d 100644
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c@@ -55,19 +55,18 @@ static inline int mmap_is_legacy(void) static unsigned long mmap_rnd(void) { - unsigned long rnd = 0; + unsigned long rnd; + + /* 8MB for 32bit, 1GB for 64bit */ + if (is_32bit_task()) + rnd = (unsigned long)get_random_int() % (1<<(23-PAGE_SHIFT)); + else + rnd = (unsigned long)get_random_int() % (1<<(30-PAGE_SHIFT)); - if (current->flags & PF_RANDOMIZE) { - /* 8MB for 32bit, 1GB for 64bit */ - if (is_32bit_task()) - rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT))); - else - rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT))); - } return rnd << PAGE_SHIFT; } -static inline unsigned long mmap_base(void) +static inline unsigned long mmap_base(unsigned long rnd) { unsigned long gap = rlimit(RLIMIT_STACK);
@@ -76,7 +75,7 @@ static inline unsigned long mmap_base(void) else if (gap > MAX_GAP) gap = MAX_GAP; - return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); + return PAGE_ALIGN(TASK_SIZE - gap - rnd); } /*
@@ -85,6 +84,11 @@ static inline unsigned long mmap_base(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:
@@ -93,7 +97,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm) mm->mmap_base = TASK_UNMAPPED_BASE; 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; } }
--
1.9.1