On Wed, Mar 20, 2019 at 02:49:38PM +0800, Xin Long wrote:
> In sctp_setsockopt_bindx()/__sctp_setsockopt_connectx(), it allocates
> memory with addrs_size which is passed from userspace. We used flag
> GFP_USER to put some more restrictions on it in Commit cacc06215271
> ("sctp: use GFP_USER for user-controlled kmalloc").
>
> However, since Commit c981f254cc82 ("sctp: use vmemdup_user() rather
> than badly open-coding memdup_user()"), vmemdup_user() has been used,
> which doesn't check GFP_USER flag when goes to vmalloc_*(). So when
> addrs_size is a huge value, it could exhaust memory and even trigger
> oom killer.
>
> This patch is to use memdup_user() instead, in which GFP_USER would
> work to limit the memory allocation with a huge addrs_size.
>
> Note we can't fix it by limiting 'addrs_size', as there's no demand
> for it from RFC.
>
> Reported-by: syzbot+ec1b7575afef85a0e5ca@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: c981f254cc82 ("sctp: use vmemdup_user() rather than badly open-coding memdup_user()")
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/socket.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 6140471..09ad5b2 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -999,7 +999,7 @@ static int sctp_setsockopt_bindx(struct sock *sk,
> if (unlikely(addrs_size <= 0))
> return -EINVAL;
>
> - kaddrs = vmemdup_user(addrs, addrs_size);
> + kaddrs = memdup_user(addrs, addrs_size);
> if (unlikely(IS_ERR(kaddrs)))
> return PTR_ERR(kaddrs);
>
> @@ -1007,7 +1007,7 @@ static int sctp_setsockopt_bindx(struct sock *sk,
> addr_buf = kaddrs;
> while (walk_size < addrs_size) {
> if (walk_size + sizeof(sa_family_t) > addrs_size) {
> - kvfree(kaddrs);
> + kfree(kaddrs);
> return -EINVAL;
> }
>
> @@ -1018,7 +1018,7 @@ static int sctp_setsockopt_bindx(struct sock *sk,
> * causes the address buffer to overflow return EINVAL.
> */
> if (!af || (walk_size + af->sockaddr_len) > addrs_size) {
> - kvfree(kaddrs);
> + kfree(kaddrs);
> return -EINVAL;
> }
> addrcnt++;
> @@ -1054,7 +1054,7 @@ static int sctp_setsockopt_bindx(struct sock *sk,
> }
>
> out:
> - kvfree(kaddrs);
> + kfree(kaddrs);
>
> return err;
> }
> @@ -1329,7 +1329,7 @@ static int __sctp_setsockopt_connectx(struct sock *sk,
> if (unlikely(addrs_size <= 0))
> return -EINVAL;
>
> - kaddrs = vmemdup_user(addrs, addrs_size);
> + kaddrs = memdup_user(addrs, addrs_size);
> if (unlikely(IS_ERR(kaddrs)))
> return PTR_ERR(kaddrs);
>
> @@ -1349,7 +1349,7 @@ static int __sctp_setsockopt_connectx(struct sock *sk,
> err = __sctp_connect(sk, kaddrs, addrs_size, flags, assoc_id);
>
> out_free:
> - kvfree(kaddrs);
> + kfree(kaddrs);
>
> return err;
> }
> --
> 2.1.0
>
>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
