[PATCH v2 2/2] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region

From: Piotr Kwapulinski
Date: Fri Nov 20 2015 - 11:42:42 EST

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.
It has no user visible effect.

Remove the code that makes no sense.

Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@xxxxxxxxx>
I made a mistake in a changelog in a previous version of this patch.
I'm Sorry for the confusion.
This patch may be considered to be applied only in case the patch
"[PATCH v2 1/2] mm: fix incorrect behavior when process virtual
address space limit is exceeded"
is not going to be accepted.

mm/mmap.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 2ce04a6..42a8259 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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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