Patch "NFS: reject request for id_legacy key without auxdata" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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;a=summary

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