Re: [Qemu-devel] [PATCH] linux-user: fix memory leak in failure path

[Peter Maydell <peter.maydell@linaro.org>]

On 28 September 2011 07:57,  <ajia@redhat.com> wrote:
> From: Alex Jia <ajia@redhat.com>
>
> Haven't released memory of 'array' and 'host_mb' in failure paths.
>
> Signed-off-by: Alex Jia <ajia@redhat.com>
> ---
>  linux-user/syscall.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 7735008..922c2a0 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -2523,8 +2523,10 @@ static inline abi_long do_semctl(int semid, int semnum, int cmd,
>        case GETALL:
>        case SETALL:
>             err = target_to_host_semarray(semid, &array, target_su.array);
> -            if (err)
> +            if (err) {
> +                free(array);
>                 return err;
> +            }
>             arg.array = array;
>             ret = get_errno(semctl(semid, semnum, cmd, arg));
>             err = host_to_target_semarray(semid, target_su.array, &array);

This is the wrong place to try to fix this. If target_to_host_semarray
fails it should free() the buffer it malloc()ed itself, not rely on
its caller to do the cleanup.

> @@ -2779,9 +2781,9 @@ static inline abi_long do_msgrcv(int msqid, abi_long msgp,
>     }
>
>     target_mb->mtype = tswapl(host_mb->mtype);
> -    free(host_mb);
>
>  end:
> +    free(host_mb);
>     if (target_mb)
>         unlock_user_struct(target_mb, msgp, 1);
>     return ret;

This change is OK.

Also I note that target_to_host_semarray is doing a plain malloc()
and not checking the return value. You should fix that while you're
doing fixes in this area.

-- PMM