Commit 49a43876 authored by Linus Torvalds's avatar Linus Torvalds Committed by Linus Torvalds
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[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: default avatarLinus Torvalds <>
parent 05d3794a
......@@ -1244,7 +1244,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
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 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
/* 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,
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