Security: round mmap hint address above mmap_min_addr

If mmap_min_addr is set and a process attempts to mmap (not fixed) with a
non-null hint address less than mmap_min_addr the mapping will fail the
security checks.  Since this is just a hint address this patch will round
such a hint address above mmap_min_addr.

gcj was found to try to be very frugal with vm usage and give hint addresses
in the 8k-32k range.  Without this patch all such programs failed and with
the patch they happily get a higher address.

This patch is wrappad in CONFIG_SECURITY since mmap_min_addr doesn't exist
without it and there would be no security check possible no matter what.  So
we should not bother compiling in this rounding if it is just a waste of
time.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
index 35622c590925..b989cb928a7c 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -829,6 +829,9 @@ unsigned long do_mmap_pgoff(struct file *file,
         void *result;
         int ret;
 
+        if (!(flags & MAP_FIXED))
+                addr = round_hint_to_min(addr);
+
         /* decide whether we should attempt the mapping, and if so what sort of
          * mapping */
         ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,