p9_client_attach(): set fid->uid correctly

it's almost always equal to current_fsuid(), but there's an exception -
if the first writeback fid is opened by non-root *and* that happens before
root has done any lookups in /, we end up doing attach for root.  The
current code leaves the resulting FID owned by root from the server POV
and by non-root from the client one.  Unfortunately, it means that e.g.
massive dcache eviction will leave that user buggered - they'll end
up redoing walks from / *and* picking that FID every time.  As soon as
they try to create something, the things will get nasty.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/net/9p/client.c b/net/9p/client.c
index 18583bb89db664bc6d432d365da084d53c4d92a3..6f4c4c88db84ecb084ca5553113d9ad2963e4985 100644 (file)
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1116,6 +1116,7 @@ struct p9_fid *p9_client_attach(struct p9_client *clnt, struct p9_fid *afid,
                fid = NULL;
                goto error;
        }
+       fid->uid = n_uname;
 
        req = p9_client_rpc(clnt, P9_TATTACH, "ddss?u", fid->fid,
                        afid ? afid->fid : P9_NOFID, uname, aname, n_uname);