net/9p: insulate the client against an invalid error code sent by a 9p server

A looney tunes server sending an invalid error code (which is !IS_ERR_VALUE)
can result in a client oops. So fix it by adding a check and converting unknown
or invalid error codes to -ESERVERFAULT.

Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 1 insertions, 6 deletions

diff --git a/net/9p/client.c b/net/9p/client.c
index 7bbd2d5ae8d3..5bf5f227dbe0 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -411,14 +411,9 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
                 if (c->dotu)
                         err = -ecode;
 
-                if (!err) {
+                if (!err || !IS_ERR_VALUE(err))
                         err = p9_errstr2errno(ename, strlen(ename));
 
-                        /* string match failed */
-                        if (!err)
-                                err = -ESERVERFAULT;
-                }
-
                 P9_DPRINTK(P9_DEBUG_9P, "<<< RERROR (%d) %s\n", -ecode, ename);
 
                 kfree(ename);