Re: [Qemu-devel] [PATCH 01/34] linux-user: Fix array bounds in errno conversion

[Laurent Vivier <laurent@vivier.eu>]

Le 12/10/2015 15:42, Riku Voipio a écrit :
> On perjantaina 11. syyskuuta 2015 13.59.29 EEST, Peter Maydell wrote:
>> On 6 September 2015 at 00:56, Timothy E Baldwin
>> <T.E.Baldwin99@members.leeds.ac.uk> wrote:
>>> Check array bounds in host_to_target_errno() and target_to_host_errno().
>>>
>>> Signed-off-by: Timothy Edward Baldwin
>>> <T.E.Baldwin99@members.leeds.ac.uk>
>>> ---
>>>  linux-user/syscall.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-) ...
>>
>> Maybe we should also check that the passed in error value is
>> not negative? (Given the errno-is-positive/syscall-return-negative
>> conventions, it's an easy mistake to make...)
> 
> I've applied a version of this patch that implements this by setting the
> function argument to unsigned
> 
> Riku
> 
> 
This patch breaks get_errno().

On a 64bit target, if errno is 22, host_to_target_errno(22) is (unsigned
int)-22 = 0xffffffea, and get_errno() is (abi_long)0xffffffea =
0x000000000xffffffea = 4294967274. It is not negative, and thus is not
an error.

host_to_target_errno() and target_to_host_errno() must stay signed.

Laurent