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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 <torvalds@osdl.org>
parent 05d3794a

mm/mmap.c

+2 −2
Original line number Diff line number Diff line
@@ -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,