On Sun, Mar 31, 2019 at 10:58 AM Xin Long <lucien.xin@xxxxxxxxx> wrote:
>
> Syzbot report a kernel-infoleak:
>
> BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
> Call Trace:
> _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
> copy_to_user include/linux/uaccess.h:174 [inline]
> sctp_getsockopt_peer_addrs net/sctp/socket.c:5911 [inline]
> sctp_getsockopt+0x1668e/0x17f70 net/sctp/socket.c:7562
> ...
> Uninit was stored to memory at:
> sctp_transport_init net/sctp/transport.c:61 [inline]
> sctp_transport_new+0x16d/0x9a0 net/sctp/transport.c:115
> sctp_assoc_add_peer+0x532/0x1f70 net/sctp/associola.c:637
> sctp_process_param net/sctp/sm_make_chunk.c:2548 [inline]
> sctp_process_init+0x1a1b/0x3ed0 net/sctp/sm_make_chunk.c:2361
> ...
> Bytes 8-15 of 16 are uninitialized
>
> It was caused by that th _pad field (the 8-15 bytes) of a v4 addr (saved in
> struct sockaddr_in) wasn't initialized, but directly copied to user memory
> in sctp_getsockopt_peer_addrs().
>
> So fix it by calling memset(addr->v4.sin_zero, 0, 8) to initialize _pad of
> sockaddr_in before copying it to user memory in sctp_v4_addr_to_user(), as
> sctp_v6_addr_to_user() does.
>
> Reported-by: syzbot+86b5c7c236a22616a72f@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Tested-by: Alexander Potapenko <glider@xxxxxxxxxx>
> ---
> net/sctp/protocol.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index 6abc8b2..951afde 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -600,6 +600,7 @@ static struct sock *sctp_v4_create_accept_sk(struct sock *sk,
> static int sctp_v4_addr_to_user(struct sctp_sock *sp, union sctp_addr *addr)
> {
> /* No address mapping for V4 sockets */
> + memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
> return sizeof(struct sockaddr_in);
> }
>
> --
> 2.1.0
>
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--
Alexander Potapenko
Software Engineer
Google Germany GmbH
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80636 München
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