4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trondmy@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;