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powerpc/mm: Enable full randomisation of memory mappings

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Do like most other architectures and provide randomisation also to
"legacy" memory mappings, by adding the random factor to
mm->mmap_base in arch_pick_mmap_layout().

See commit 8b8addf891 ("x86/mm/32: Enable full randomization on
i386 and X86_32") for all explanations and benefits of that mmap
randomisation.

At the moment, slice_find_area_bottomup() doesn't use mm->mmap_base
but uses the fixed TASK_UNMAPPED_BASE instead.
slice_find_area_bottomup() being used as a fallback to
slice_find_area_topdown(), it can't use mm->mmap_base
directly.

Instead of always using TASK_UNMAPPED_BASE as base address, leave
it to the caller. When called from slice_find_area_topdown()
TASK_UNMAPPED_BASE is used. Otherwise mm->mmap_base is used.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/417fb10dde828534c73a03138b49621d74f4e5be.1649523076.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2022-04-09 19:17:35 +02:00 committed by Michael Ellerman
parent ab57bd7570
commit 5cf7f9a0a5
2 changed files with 8 additions and 12 deletions
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18
arch/powerpc/mm/book3s64/slice.c
View File

@ -276,20 +276,18 @@ static bool slice_scan_available(unsigned long addr,
}
static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
unsigned long len,
unsigned long addr, unsigned long len,
const struct slice_mask *available,
int psize, unsigned long high_limit)
{
int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
unsigned long addr, found, next_end;
unsigned long found, next_end;
struct vm_unmapped_area_info info;
info.flags = 0;
info.length = len;
info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
info.align_offset = 0;
addr = TASK_UNMAPPED_BASE;
/*
* Check till the allow max value for this mmap request
*/
@ -322,12 +320,12 @@ static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
}
static unsigned long slice_find_area_topdown(struct mm_struct *mm,
unsigned long len,
unsigned long addr, unsigned long len,
const struct slice_mask *available,
int psize, unsigned long high_limit)
{
int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
unsigned long addr, found, prev;
unsigned long found, prev;
struct vm_unmapped_area_info info;
unsigned long min_addr = max(PAGE_SIZE, mmap_min_addr);
@ -335,8 +333,6 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
info.length = len;
info.align_mask = PAGE_MASK & ((1ul << pshift) - 1);
info.align_offset = 0;
addr = mm->mmap_base;
/*
* If we are trying to allocate above DEFAULT_MAP_WINDOW
* Add the different to the mmap_base.
@ -377,7 +373,7 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm,
* can happen with large stack limits and large mmap()
* allocations.
*/
return slice_find_area_bottomup(mm, len, available, psize, high_limit);
return slice_find_area_bottomup(mm, TASK_UNMAPPED_BASE, len, available, psize, high_limit);
}
@ -386,9 +382,9 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
int topdown, unsigned long high_limit)
{
if (topdown)
return slice_find_area_topdown(mm, len, mask, psize, high_limit);
return slice_find_area_topdown(mm, mm->mmap_base, len, mask, psize, high_limit);
else
return slice_find_area_bottomup(mm, len, mask, psize, high_limit);
return slice_find_area_bottomup(mm, mm->mmap_base, len, mask, psize, high_limit);
}
static inline void slice_copy_mask(struct slice_mask *dst,

2
arch/powerpc/mm/mmap.c
View File

@ -96,7 +96,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
* bit is set, or if the expected stack growth is unlimited:
*/
if (mmap_is_legacy(rlim_stack)) {
mm->mmap_base = TASK_UNMAPPED_BASE;
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
mm->mmap_base = mmap_base(random_factor, rlim_stack);