Re: qemu-sockets: account for trailing \0 byte in unix socket pathname

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

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Hi

On Tue, Aug 31, 2021 at 3:00 AM Michael Tokarev <mjt@tls.msk.ru> wrote:

> Linux kernel can return size of af_unix socket to be
> one byte larger than sockaddr_un structure - adding
> the trailing zero byte.
>
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
> Fixes: 4cfd970ec188558daa6214f26203fe553fb1e01f (first in 6.1.0)
> Cc: qemu-stable@nongnu.org
>
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index f2f3676d1f..83926dc2bc 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -1345,8 +1345,9 @@ socket_sockaddr_to_address_unix(struct
> sockaddr_storage *sa,
>      SocketAddress *addr;
>      struct sockaddr_un *su = (struct sockaddr_un *)sa;
>
> +    /* kernel might have added \0 terminator to non-abstract socket */
>      assert(salen >= sizeof(su->sun_family) + 1 &&
> -           salen <= sizeof(struct sockaddr_un));
> +           salen <= sizeof(struct sockaddr_un) + su->sun_path[0] ? 1 : 0);
>
>
Looks right, but we may want to drop the upper bound check altogether. I
thought the path must always fit the sockaddr_un, but since that's not the
case it's only harmful here.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

     addr = g_new0(SocketAddress, 1);
>      addr->type = SOCKET_ADDRESS_TYPE_UNIX;
>
>

-- 
Marc-André Lureau

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