[Qemu-devel] AIO error case

[Nishanth Aravamudan via Qemu-devel]

Hi!

I'm tracking an error case in the native AIO path, and was wondering if
there was a latent (albeit possibly hard to hit) bug. Specifically
util/async.c::aio_get_linux_aio:

#ifdef CONFIG_LINUX_AIO
LinuxAioState *aio_get_linux_aio(AioContext *ctx)
{
    if (!ctx->linux_aio) {
        ctx->linux_aio = laio_init();
        laio_attach_aio_context(ctx->linux_aio, ctx);
    }
    return ctx->linux_aio;
}
#endif

laio_init() can in certain conditions return NULL, but that's not checked
here and then the NULL result is passed directly into
laio_attach_aio_context, which dereferences it without checking that the
pointer is valid.

I'm not sure what is appropriate if laio_init() returns NULL, returning
NULL back to the caller of aio_get_linux_aio() has its own issues, because
those callers don't seem to check its return value either.

Thanks in advance!
-Nish