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sunrpc: Fix misplaced barrier in call_decode 

Fix a misplaced barrier in call_decode. The struct rpc_rqst is modified
as follows by xprt_complete_rqst:

req->rq_private_buf.len = copied;
/* Ensure all writes are done before we update */
/* req->rq_reply_bytes_recvd */
smp_wmb();
req->rq_reply_bytes_recvd = copied;

And currently read as follows by call_decode:

smp_rmb(); // misplaced
if (!req->rq_reply_bytes_recvd)
   goto out;
req->rq_rcv_buf.len = req->rq_private_buf.len;

This patch places the smp_rmb after the if to ensure that
rq_reply_bytes_recvd and rq_private_buf.len are read in order.

Fixes: 9ba828861c ("SUNRPC: Don't try to parse incomplete RPC messages")
Signed-off-by: Baptiste Lepers <baptiste.lepers@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Baptiste Lepers 2021-05-01 14:10:51 +10:00 committed by Trond Myklebust
parent d9092b4bb2
commit f8f7e0fb22
1 changed files with 5 additions and 6 deletions
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11
net/sunrpc/clnt.c
View File

@ -2456,12 +2456,6 @@ call_decode(struct rpc_task *task)
task->tk_flags &= ~RPC_CALL_MAJORSEEN;
}
/*
* Ensure that we see all writes made by xprt_complete_rqst()
* before it changed req->rq_reply_bytes_recvd.
*/
smp_rmb();
/*
* Did we ever call xprt_complete_rqst()? If not, we should assume
* the message is incomplete.
@ -2470,6 +2464,11 @@ call_decode(struct rpc_task *task)
if (!req->rq_reply_bytes_recvd)
goto out;
/* Ensure that we see all writes made by xprt_complete_rqst()
* before it changed req->rq_reply_bytes_recvd.
*/
smp_rmb();
req->rq_rcv_buf.len = req->rq_private_buf.len;
trace_rpc_xdr_recvfrom(task, &req->rq_rcv_buf);