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;
--
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