To ensure that all memory allocations comply with the new MAP_BELOW_HINT flag, set the high_limit in vm_unmapped_area() to the hint address + length at most. All callers to this function set the high_limit to something reasonable, usually with space for a random offset and a gap for the stack. To respect the provided high_limit, take the minimum of hint+length and the given high_limit.
Signed-off-by: Charlie Jenkins charlie@rivosinc.com --- mm/mmap.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/mm/mmap.c b/mm/mmap.c index 34ba0db23678..459ad380c673 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1766,6 +1766,9 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info) { unsigned long addr;
+ if (info->hint != 0 && info->mmap_flags & MAP_BELOW_HINT) + info->high_limit = MIN(info->high_limit, info->hint + info->length); + if (info->flags & VM_UNMAPPED_AREA_TOPDOWN) addr = unmapped_area_topdown(info); else