Commit bc36f701 authored Jan 14, 2016 by Piotr Kwapulinski Committed by Linus Torvalds Jan 14, 2016

mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region



The following flag comparison in mmap_region makes no sense:

    if (!(vm_flags & MAP_FIXED))
        return -ENOMEM;

The condition is always false and thus the above "return -ENOMEM" is
never executed.  The vm_flags must not be compared with MAP_FIXED flag.
The vm_flags may only be compared with VM_* flags.  MAP_FIXED has the
same value as VM_MAYREAD.

Hitting the rlimit is a slow path and find_vma_intersection should
realize that there is no overlapping VMA for !MAP_FIXED case pretty
quickly.

Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 9f6c399d

mm/mmap.c

+0 −3

Original line number	Diff line number	Diff line
		@@ -1551,9 +1551,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
		* MAP_FIXED may remove pages of mappings that intersects with
		* requested mapping. Account for the pages it would unmap.
		*/
		if (!(vm_flags & MAP_FIXED))
		return -ENOMEM;

		nr_pages = count_vma_pages_range(mm, addr, addr + len);

		if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))

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