Re: [Qemu-devel] [PATCH for-2.7] linux-user: Fix llseek with high bit of offset_low set

[Chanho Park <parkch98@gmail.com>]

It works perfectly.
Thanks.

Tested-by: Chanho Park <parkch98@gmail.com>

On Fri, Aug 12, 2016 at 2:59 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
> The llseek syscall takes two 32-bit arguments, offset_high
> and offset_low, which must be combined to form a single
> 64-bit offset. Unfortunately we were combining them with
>    (uint64_t)arg2 << 32) | arg3
> and arg3 is a signed type; this meant that when promoting
> arg3 to a 64-bit type it would be sign-extended. The effect
> was that if the offset happened to have bit 31 set then
> this bit would get sign-extended into all of bits 63..32.
> Explicitly cast arg3 to abi_ulong to avoid the erroneous
> sign extension.
>
> Reported-by: Chanho Park <parkch98@gmail.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> Long-standing bug and we're quite close to 2.7 but the
> fix is trivial so if somebody would like to review it
> I think we could put it in...
>
>  linux-user/syscall.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index ebdb753..b4e21d3 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -9406,7 +9406,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>          {
>              int64_t res;
>  #if !defined(__NR_llseek)
> -            res = lseek(arg1, ((uint64_t)arg2 << 32) | arg3, arg5);
> +            res = lseek(arg1, ((uint64_t)arg2 << 32) | (abi_ulong)arg3, arg5);
>              if (res == -1) {
>                  ret = get_errno(res);
>              } else {
> --
> 2.7.4
>



-- 
Best Regards,
Chanho Park