net/9p: fix response size check in p9_check_errors()

Since commit 60ece0833b6c ("net/9p: allocate appropriate reduced message
buffers") it is no longer appropriate to check server's response size
against msize. Check against the previously allocated buffer capacity
instead.

- Omit this size check entirely for zero-copy messages, as those always
  allocate 4k (P9_ZC_HDR_SZ) linear buffers which are not used for actual
  payload and can be much bigger than 4k.

- Replace p9_debug() by pr_err() to make sure this message is always
  printed in case this error is triggered.

- Add 9p message type to error message to ease investigation.

Link: https://lkml.kernel.org/r/e0edec84b1c80119ae937ce854b4f5f6dbe2d08c.1669144861.git.linux_oss@crudebyte.com
Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

diff --git a/net/9p/client.c b/net/9p/client.c
index a2b4a965a5a99e82ac881299bbd917feed0ca459..7b2a997662d9cc5f79aab8f46ccecafda30849f0 100644 (file)
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -519,10 +519,9 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
        int ecode;
 
        err = p9_parse_header(&req->rc, NULL, &type, NULL, 0);
-       if (req->rc.size >= c->msize) {
-               p9_debug(P9_DEBUG_ERROR,
-                        "requested packet size too big: %d\n",
-                        req->rc.size);
+       if (req->rc.size > req->rc.capacity && !req->rc.zc) {
+               pr_err("requested packet size too big: %d does not fit %zu (type=%d)\n",
+                      req->rc.size, req->rc.capacity, req->rc.id);
                return -EIO;
        }
        /* dump the response from server