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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: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Linus Torvalds 2005-05-18 15:39:33 -07:00 committed by Linus Torvalds
parent 05d3794aa8
commit 49a43876b9
1 changed files with 2 additions and 2 deletions
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4
mm/mmap.c
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@ -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,