4.4-stable review patch. If anyone has any objections, please let me know.
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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;