On 02/13/2015 05:43 PM, Trond Myklebust wrote:
> 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?
I'll make a pull request.
Thanks,
Anna
>
> Cheers
> Trond
>
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