9p: cope with bogus responses from server in p9_client_{read,write}

if server claims to have written/read more than we'd told it to,
warn and cap the claimed byte count to avoid advancing more than
we are ready to.

1 files changed, 8 insertions, 0 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index 81925b923318..498454b3c06c 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1583,6 +1583,10 @@ p9_client_read(struct p9_fid *fid, u64 offset, struct iov_iter *to, int *err)
                         p9_free_req(clnt, req);
                         break;
                 }
+                if (rsize < count) {
+                        pr_err("bogus RREAD count (%d > %d)\n", count, rsize);
+                        count = rsize;
+                }
 
                 p9_debug(P9_DEBUG_9P, "<<< RREAD count %d\n", count);
                 if (!count) {
@@ -1650,6 +1654,10 @@ p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
                         p9_free_req(clnt, req);
                         break;
                 }
+                if (rsize < count) {
+                        pr_err("bogus RWRITE count (%d > %d)\n", count, rsize);
+                        count = rsize;
+                }
 
                 p9_debug(P9_DEBUG_9P, "<<< RWRITE count %d\n", count);