tree 6e753db66f4404526d6c22a41a3a050dc156db72
parent 300613e523d53f346f8ff0256921e289da39ed7b
author Paul Mackerras <paulus@samba.org> 1207977659 +1000
committer Paul Mackerras <paulus@samba.org> 1208258537 +1000

[LMB] Restructure allocation loops to avoid unsigned underflow

There is a potential bug in __lmb_alloc_base where we subtract `size'
from the base address of a reserved region without checking whether
the subtraction could wrap around and produce a very large unsigned
value.  In fact it probably isn't possible to hit the bug in practice
since it would only occur in the situation where we can't satisfy the
allocation request and there is a reserved region starting at 0.

This fixes the potential bug by breaking out of the loop when we get
to the point where the base of the reserved region is less than the
size requested.  This also restructures the loop to be a bit easier to
follow.

The same logic got copied into lmb_alloc_nid_unreserved, so this makes
a similar change there.  Here the bug is more likely to be hit because
the outer loop  (in lmb_alloc_nid) goes through the memory regions in
increasing order rather than decreasing order as __lmb_alloc_base
does, and we are therefore more likely to hit the case where we are
testing against a reserved region with a base address of 0.

Signed-off-by: Paul Mackerras <paulus@samba.org>