[RFC PATCH v6 12/20] ceph: send altname in MClientRequest

Jeff Layton
2021-04-13T17:51:05Z

In the event that we have a filename longer than CEPH_NOHASH_NAME_MAX,
we'll need to hash the tail of the filename. The client however will
still need to know the full name of the file if it has a key.

To support this, the MClientRequest field has grown a new alternate_name
field that we populate with the full (binary) crypttext of the filename.
This is then transmitted to the clients in readdir or traces as part of
the dentry lease.

Add support for populating this field when the filenames are very long.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/ceph/mds_client.c | 79 +++++++++++++++++++++++++++++++++++++++++---
fs/ceph/mds_client.h | 2 ++
2 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 77181a1fc900..2bcef4ddbe00 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -892,6 +892,7 @@ void ceph_mdsc_release_request(struct kref *kref)
put_cred(req->r_cred);
if (req->r_pagelist)
ceph_pagelist_release(req->r_pagelist);
+ kfree(req->r_altname);
put_request_session(req);
ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
WARN_ON_ONCE(!list_empty(&req->r_wait));
@@ -2416,11 +2417,66 @@ static int encode_encrypted_fname(const struct inode *parent, struct dentry *den
dout("base64-encoded ciphertext name = %.*s\n", len, buf);
return elen;
}
+
+static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
+{
+ struct inode *dir = req->r_parent;
+ struct dentry *dentry = req->r_dentry;
+ u8 *cryptbuf = NULL;
+ u32 len = 0;
+ int ret = 0;
+
+ /* only encode if we have parent and dentry */
+ if (!dir || !dentry)
+ goto success;
+
+ /* No-op unless this is encrypted */
+ if (!IS_ENCRYPTED(dir))
+ goto success;
+
+ ret = __fscrypt_prepare_readdir(dir);
+ if (ret)
+ return ERR_PTR(ret);
+
+ /* No key? Just ignore it. */
+ if (!fscrypt_has_encryption_key(dir))
+ goto success;
+
+ if (!fscrypt_fname_encrypted_size(dir, dentry->d_name.len, NAME_MAX, &len)) {
+ WARN_ON_ONCE(1);
+ return ERR_PTR(-ENAMETOOLONG);
+ }
+
+ /* No need to append altname if name is short enough */
+ if (len <= CEPH_NOHASH_NAME_MAX) {
+ len = 0;
+ goto success;
+ }
+
+ cryptbuf = kmalloc(len, GFP_KERNEL);
+ if (!cryptbuf)
+ return ERR_PTR(-ENOMEM);
+
+ ret = fscrypt_fname_encrypt(dir, &dentry->d_name, cryptbuf, len);
+ if (ret) {
+ kfree(cryptbuf);
+ return ERR_PTR(ret);
+ }
+success:
+ *plen = len;
+ return cryptbuf;
+}
#else
static int encode_encrypted_fname(const struct inode *parent, struct dentry *dentry, char *buf)
{
return -EOPNOTSUPP;
}
+
+static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
+{
+ *plen = 0;
+ return NULL;
+}
#endif

/**
@@ -2635,7 +2691,7 @@ static int set_request_path_attr(struct inode *rinode, struct dentry *rdentry,
return r;
}

-static void encode_timestamp_and_gids(void **p,
+static void encode_mclientrequest_tail(void **p,
const struct ceph_mds_request *req)
{
struct ceph_timespec ts;
@@ -2644,11 +2700,16 @@ static void encode_timestamp_and_gids(void **p,
ceph_encode_timespec64(&ts, &req->r_stamp);
ceph_encode_copy(p, &ts, sizeof(ts));

- /* gid_list */
+ /* v4: gid_list */
ceph_encode_32(p, req->r_cred->group_info->ngroups);
for (i = 0; i < req->r_cred->group_info->ngroups; i++)
ceph_encode_64(p, from_kgid(&init_user_ns,
req->r_cred->group_info->gid[i]));
+
+ /* v5: altname */
+ ceph_encode_32(p, req->r_altname_len);
+ if (req->r_altname_len)
+ ceph_encode_copy(p, req->r_altname, req->r_altname_len);
}

/*
@@ -2693,10 +2754,18 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
goto out_free1;
}

+ req->r_altname = get_fscrypt_altname(req, &req->r_altname_len);
+ if (IS_ERR(req->r_altname)) {
+ msg = ERR_CAST(req->r_altname);
+ req->r_altname = NULL;
+ goto out_free2;
+ }
+
len = legacy ? sizeof(*head) : sizeof(struct ceph_mds_request_head);
len += pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64)) +
sizeof(struct ceph_timespec);
len += sizeof(u32) + (sizeof(u64) * req->r_cred->group_info->ngroups);
+ len += sizeof(u32) + req->r_altname_len;

/* calculate (max) length for cap releases */
len += sizeof(struct ceph_mds_request_release) *
@@ -2727,7 +2796,7 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
} else {
struct ceph_mds_request_head *new_head = msg->front.iov_base;

- msg->hdr.version = cpu_to_le16(4);
+ msg->hdr.version = cpu_to_le16(5);
new_head->version = cpu_to_le16(CEPH_MDS_REQUEST_HEAD_VERSION);
head = (struct ceph_mds_request_head_old *)&new_head->oldest_client_tid;
p = msg->front.iov_base + sizeof(*new_head);
@@ -2778,7 +2847,7 @@ static struct ceph_msg *create_request_message(struct ceph_mds_session *session,

head->num_releases = cpu_to_le16(releases);

- encode_timestamp_and_gids(&p, req);
+ encode_mclientrequest_tail(&p, req);

if (WARN_ON_ONCE(p > end)) {
ceph_msg_put(msg);
@@ -2887,7 +2956,7 @@ static int __prepare_send_request(struct ceph_mds_session *session,
rhead->num_releases = 0;

p = msg->front.iov_base + req->r_request_release_offset;
- encode_timestamp_and_gids(&p, req);
+ encode_mclientrequest_tail(&p, req);

msg->front.iov_len = p - msg->front.iov_base;
msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index 676fd994f6b8..597d8d8053c0 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -280,6 +280,8 @@ struct ceph_mds_request {
struct mutex r_fill_mutex;

union ceph_mds_request_args r_args;
+ u8 *r_altname; /* fscrypt binary crypttext for long filenames */
+ u32 r_altname_len; /* length of r_altname */
int r_fmode; /* file mode, if expecting cap */
const struct cred *r_cred;
int r_request_release_offset;
--
2.30.2