On Thu, 2015-02-12 at 10:14 -0500, Chuck Lever wrote:
> Dan Carpenter's static checker pointed out:
>
> net/sunrpc/xprtrdma/rpc_rdma.c:879 rpcrdma_reply_handler()
> warn: can 'credits' be negative?
>
> "credits" is defined as an int. The credits value comes from the
> server as a 32-bit unsigned integer.
>
> A malicious or broken server can plant a large unsigned integer in
> that field which would result in an underflow in the following
> logic, potentially triggering a deadlock of the mount point by
> blocking the client from issuing more RPC requests.
>
> net/sunrpc/xprtrdma/rpc_rdma.c:
>
> 876 credits = be32_to_cpu(headerp->rm_credit);
> 877 if (credits == 0)
> 878 credits = 1; /* don't deadlock */
> 879 else if (credits > r_xprt->rx_buf.rb_max_requests)
> 880 credits = r_xprt->rx_buf.rb_max_requests;
> 881
> 882 cwnd = xprt->cwnd;
> 883 xprt->cwnd = credits << RPC_CWNDSHIFT;
> 884 if (xprt->cwnd > cwnd)
> 885 xprt_release_rqst_cong(rqst->rq_task);
>
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Fixes: eba8ff660b2d ("xprtrdma: Move credit update to RPC . . .")
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> net/sunrpc/xprtrdma/rpc_rdma.c | 3 ++-
> net/sunrpc/xprtrdma/xprt_rdma.h | 2 +-
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index 7e9acd9..91ffde8 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -738,8 +738,9 @@ rpcrdma_reply_handler(struct rpcrdma_rep *rep)
> struct rpc_xprt *xprt = rep->rr_xprt;
> struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
> __be32 *iptr;
> - int credits, rdmalen, status;
> + int rdmalen, status;
> unsigned long cwnd;
> + u32 credits;
>
> /* Check status. If bad, signal disconnect and return rep to pool */
> if (rep->rr_len == ~0U) {
> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> index d1b7039..0a16fb6 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -285,7 +285,7 @@ rpcr_to_rdmar(struct rpc_rqst *rqst)
> */
> struct rpcrdma_buffer {
> spinlock_t rb_lock; /* protects indexes */
> - int rb_max_requests;/* client max requests */
> + u32 rb_max_requests;/* client max requests */
> struct list_head rb_mws; /* optional memory windows/fmrs/frmrs */
> struct list_head rb_all;
> int rb_send_index;
>
Anna, do you want me to take this one directly, or are you preparing a
pull request?
Cheers
Trond
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