[PATCH v3] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region

From: Piotr Kwapulinski
Date: Mon Nov 23 2015 - 12:37:26 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.
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.

Remove the code that makes no sense.

Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@xxxxxxxxx>
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))

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/