This is a note to let you know that I've just added the patch titled

NFS: reject request for id_legacy key without auxdata

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: nfs-reject-request-for-id_legacy-key-without-auxdata.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

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: NFS: reject request for id_legacy key without auxdata

From: Eric Biggers ebiggers@google.com

commit 49686cbbb3ebafe42e63868222f269d8053ead00 upstream.

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 Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Trond Myklebust trondmy@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- fs/nfs/nfs4idmap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -567,9 +567,13 @@ static int nfs_idmap_legacy_upcall(struc 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;

Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.9/nfs-reject-request-for-id_legacy-key-without-auxdata.patch