9p/net: return error on bogus (longer than requested) replies

Up until now we've been considering longer than requested replies as
acceptable, printing a message and just truncating the data,
but it makes more sense to consider these an error.

Make these fail with EIO instead.

Suggested-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Message-ID: <20250317-p9_bogus_io_error-v1-1-9639f6d1561f@codewreck.org>

diff --git a/net/9p/client.c b/net/9p/client.c
index 99e9a55199e851ae1b2c94035dddb33fe4bd43ef..a2e5ff161562b58fc05118dbae697f326501be11 100644 (file)
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1594,7 +1594,9 @@ p9_client_read_once(struct p9_fid *fid, u64 offset, struct iov_iter *to,
        }
        if (rsize < received) {
                pr_err("bogus RREAD count (%u > %u)\n", received, rsize);
-               received = rsize;
+               *err = -EIO;
+               p9_req_put(clnt, req);
+               return 0;
        }
 
        p9_debug(P9_DEBUG_9P, "<<< RREAD count %u\n", received);
@@ -1661,7 +1663,10 @@ p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
                }
                if (rsize < written) {
                        pr_err("bogus RWRITE count (%u > %u)\n", written, rsize);
-                       written = rsize;
+                       *err = -EIO;
+                       iov_iter_revert(from, count - iov_iter_count(from));
+                       p9_req_put(clnt, req);
+                       break;
                }
 
                p9_debug(P9_DEBUG_9P, "<<< RWRITE count %u\n", written);
@@ -1713,7 +1718,7 @@ p9_client_write_subreq(struct netfs_io_subrequest *subreq)
 
        if (written > len) {
                pr_err("bogus RWRITE count (%d > %u)\n", written, len);
-               written = len;
+               written = -EIO;
        }
 
        p9_debug(P9_DEBUG_9P, "<<< RWRITE count %d\n", len);
@@ -2145,7 +2150,8 @@ int p9_client_readdir(struct p9_fid *fid, char *data, u32 count, u64 offset)
        }
        if (rsize < count) {
                pr_err("bogus RREADDIR count (%u > %u)\n", count, rsize);
-               count = rsize;
+               err = -EIO;
+               goto free_and_error;
        }
 
        p9_debug(P9_DEBUG_9P, "<<< RREADDIR count %u\n", count);