The patch below does not apply to the 3.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 49686cbbb3ebafe42e63868222f269d8053ead00 Mon Sep 17 00:00:00 2001
From: Eric Biggers ebiggers@google.com Date: Fri, 19 Jan 2018 15:15:34 -0800 Subject: [PATCH] NFS: reject request for id_legacy key without auxdata
nfs_idmap_legacy_upcall() is supposed to be called with 'aux' pointing to a 'struct idmap', via the call to request_key_with_auxdata() in nfs_idmap_request_key().
However it can also be reached via the request_key() system call in which case 'aux' will be NULL, causing a NULL pointer dereference in nfs_idmap_prepare_pipe_upcall(), assuming that the key description is valid enough to get that far.
Fix this by making nfs_idmap_legacy_upcall() negate the key if no auxdata is provided.
As usual, this bug was found by syzkaller. A simple reproducer using the command-line keyctl program is:
keyctl request2 id_legacy uid:0 '' @s
Fixes: 57e62324e469 ("NFS: Store the legacy idmapper result in the keyring") Reported-by: syzbot+5dfdbcf7b3eb5912abbb@syzkaller.appspotmail.com Cc: stable@vger.kernel.org # v3.4+ Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Trond Myklebust trondmy@gmail.com
diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c index 30426c1a1bbd..22dc30a679a0 100644 --- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -568,9 +568,13 @@ static int nfs_idmap_legacy_upcall(struct key_construction *cons, struct idmap_msg *im; struct idmap *idmap = (struct idmap *)aux; struct key *key = cons->key; - int ret = -ENOMEM; + int ret = -ENOKEY; + + if (!aux) + goto out1;
/* msg and im are freed in idmap_pipe_destroy_msg */ + ret = -ENOMEM; data = kzalloc(sizeof(*data), GFP_KERNEL); if (!data) goto out1;