[PATCH] prevent NULL mmap in topdown model
Prevent the topdown allocator from allocating mmap areas all the way
down to address zero.
We still allow a MAP_FIXED mapping of page 0 (needed for various things,
ranging from Wine and DOSEMU to people who want to allow speculative
loads off a NULL pointer).
Tested by Chris Wright.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/mmap.c b/mm/mmap.c
index 01f9793..63df2d6 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1244,7 +1244,7 @@
addr = mm->free_area_cache;
/* make sure it can fit in the remaining address space */
- if (addr >= len) {
+ if (addr > len) {
vma = find_vma(mm, addr-len);
if (!vma || addr <= vma->vm_start)
/* remember the address as a hint for next time */
@@ -1266,7 +1266,7 @@
/* try just below the current vma->vm_start */
addr = vma->vm_start-len;
- } while (len <= vma->vm_start);
+ } while (len < vma->vm_start);
/*
* A failed mmap() very likely causes application failure,