diff options
| author | Michel Lespinasse <walken@google.com> | 2013-02-22 16:32:46 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-02-23 17:50:11 -0800 |
| commit | 1869305009857cdeaabe6283bcdc2359c5784543 (patch) | |
| tree | a8a500c71e7aa3a645322635f3d591c16601af27 /include/linux/mman.h | |
| parent | cea10a19b7972a1954c4a2d05a7de8db48b444fb (diff) | |
mm: introduce VM_POPULATE flag to better deal with racy userspace programs
The vm_populate() code populates user mappings without constantly
holding the mmap_sem. This makes it susceptible to racy userspace
programs: the user mappings may change while vm_populate() is running,
and in this case vm_populate() may end up populating the new mapping
instead of the old one.
In order to reduce the possibility of userspace getting surprised by
this behavior, this change introduces the VM_POPULATE vma flag which
gets set on vmas we want vm_populate() to work on. This way
vm_populate() may still end up populating the new mapping after such a
race, but only if the new mapping is also one that the user has
requested (using MAP_SHARED, MAP_LOCKED or mlock) to be populated.
Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Tested-by: Andy Lutomirski <luto@amacapital.net>
Cc: Greg Ungerer <gregungerer@westnet.com.au>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mman.h')
| -rw-r--r-- | include/linux/mman.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/mman.h b/include/linux/mman.h index 9aa863da287..61c7a87e5d2 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -79,6 +79,8 @@ calc_vm_flag_bits(unsigned long flags) { return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) | _calc_vm_trans(flags, MAP_DENYWRITE, VM_DENYWRITE ) | - _calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ); + ((flags & MAP_LOCKED) ? (VM_LOCKED | VM_POPULATE) : 0) | + (((flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE) ? + VM_POPULATE : 0); } #endif /* _LINUX_MMAN_H */ |