Re: [Qemu-devel] [PATCH] mmap: add check if requested memory area fits target address space

[andrzej zaborowski]

2008/10/27 Kirill A. Shutemov <address@hidden>:
> On Mon, Oct 27, 2008 at 02:08:52PM +0100, andrzej zaborowski wrote:
>> On 17/10/2008, Kirill A. Shutemov <address@hidden> wrote:
>> > Signed-off-by: Kirill A. Shutemov <address@hidden>
>> >  ---
>> >   linux-user/mmap.c |    5 +++++
>> >   1 files changed, 5 insertions(+), 0 deletions(-)
>> >
>> >  diff --git a/linux-user/mmap.c b/linux-user/mmap.c
>> >  index bc20f4b..9a2f355 100644
>> >  --- a/linux-user/mmap.c
>> >  +++ b/linux-user/mmap.c
>> >  @@ -388,6 +388,11 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, 
>> > int prot,
>> >          end = start + len;
>> >          real_end = HOST_PAGE_ALIGN(end);
>> >
>> >  +        if ((unsigned long)start + len > (abi_ulong) -1) {
>> >  +            errno = EINVAL;
>> >  +            goto fail;
>> >  +        }
>>
>> I'm being picky but this would prevent the last byte from being used?
>> :p  (or the last page because len is aligned?)
>
> No, it returns error if start + len is more than 0xFFFFFFFF (32-bit
> target).
>
>>
>> I'm not sure unsigned long is the best choice.
>
> Why?

I may be misunderstanding but I think the range of valid addresses
should depend on target word size, not host (even if the combination
where it matters is not yet supported).  On a 32-bit host the
condition is always false.

Cheers