The following bit in ceph_msg_revoke_incoming() is unsafe:
struct ceph_connection *con = msg->con;
if (!con)
return;
mutex_lock(&con->mutex);
<more msg->con use>
There is nothing preventing con from getting destroyed right after
msg->con test. One easy way to reproduce this is to disable message
signing only on the server side and try to map an image. The system
will go into a
libceph: read_partial_message ffff880073f0ab68 signature check failed
libceph: osd0 192.168.255.155:6801 bad crc/signature
libceph: read_partial_message ffff880073f0ab68 signature check failed
libceph: osd0 192.168.255.155:6801 bad crc/signature
loop which has to be interrupted with Ctrl-C. Hit Ctrl-C and you are
likely to end up with a random GP fault if the reset handler executes
"within" ceph_msg_revoke_incoming():
<yet another reply w/o a signature>
...
<Ctrl-C>
rbd_obj_request_end
ceph_osdc_cancel_request
__unregister_request
ceph_osdc_put_request
ceph_msg_revoke_incoming
...
osd_reset
__kick_osd_requests
__reset_osd
remove_osd
ceph_con_close
reset_connection
<clear con->in_msg->con>
<put con ref>
put_osd
<free osd/con>
<msg->con use> <-- !!!
If ceph_msg_revoke_incoming() executes "before" the reset handler,
osd/con will be leaked because ceph_msg_revoke_incoming() clears
con->in_msg but doesn't put con ref, while reset_connection() only puts
con ref if con->in_msg != NULL.
The current msg->con scheme was introduced by commits 38941f8031bf
("libceph: have messages point to their connection") and 92ce034b5a74
("libceph: have messages take a connection reference"), which defined
when messages get associated with a connection and when that
association goes away. Part of the problem is that this association is
supposed to go away in much too many places; closing this race entirely
requires either a rework of the existing or an addition of a new layer
of synchronization.
In lieu of that, we can make it *much* less likely to hit by
disassociating messages only on their destruction and resend through
a different connection. This makes the code simpler and is probably
a good thing to do regardless - this patch adds a msg_con_set() helper
which is is called from only three places: ceph_con_send() and
ceph_con_in_msg_alloc() to set msg->con and ceph_msg_release() to clear
it.
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
---
net/ceph/messenger.c | 45 ++++++++++++++++++++-------------------------
net/ceph/osd_client.c | 3 ---
2 files changed, 20 insertions(+), 28 deletions(-)
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 0cc5608b2c8f..9981039ef4ff 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -637,9 +637,6 @@ static int con_close_socket(struct ceph_connection *con)
static void ceph_msg_remove(struct ceph_msg *msg)
{
list_del_init(&msg->list_head);
- BUG_ON(msg->con == NULL);
- msg->con->ops->put(msg->con);
- msg->con = NULL;
ceph_msg_put(msg);
}
@@ -662,15 +659,14 @@ static void reset_connection(struct ceph_connection *con)
if (con->in_msg) {
BUG_ON(con->in_msg->con != con);
- con->in_msg->con = NULL;
ceph_msg_put(con->in_msg);
con->in_msg = NULL;
- con->ops->put(con);
}
con->connect_seq = 0;
con->out_seq = 0;
if (con->out_msg) {
+ BUG_ON(con->out_msg->con != con);
ceph_msg_put(con->out_msg);
con->out_msg = NULL;
}
@@ -2438,13 +2434,10 @@ static int read_partial_message(struct ceph_connection *con)
*/
static void process_message(struct ceph_connection *con)
{
- struct ceph_msg *msg;
+ struct ceph_msg *msg = con->in_msg;
BUG_ON(con->in_msg->con != con);
- con->in_msg->con = NULL;
- msg = con->in_msg;
con->in_msg = NULL;
- con->ops->put(con);
/* if first message, set peer_name */
if (con->peer_name.type == 0)
@@ -2918,10 +2911,8 @@ static void con_fault(struct ceph_connection *con)
if (con->in_msg) {
BUG_ON(con->in_msg->con != con);
- con->in_msg->con = NULL;
ceph_msg_put(con->in_msg);
con->in_msg = NULL;
- con->ops->put(con);
}
/* Requeue anything that hasn't been acked */
@@ -2977,6 +2968,15 @@ void ceph_messenger_fini(struct ceph_messenger *msgr)
}
EXPORT_SYMBOL(ceph_messenger_fini);
+static void msg_con_set(struct ceph_msg *msg, struct ceph_connection *con)
+{
+ if (msg->con)
+ msg->con->ops->put(msg->con);
+
+ msg->con = con ? con->ops->get(con) : NULL;
+ BUG_ON(msg->con != con);
+}
+
static void clear_standby(struct ceph_connection *con)
{
/* come back from STANDBY? */
@@ -3008,9 +3008,7 @@ void ceph_con_send(struct ceph_connection *con, struct ceph_msg *msg)
return;
}
- BUG_ON(msg->con != NULL);
- msg->con = con->ops->get(con);
- BUG_ON(msg->con == NULL);
+ msg_con_set(msg, con);
BUG_ON(!list_empty(&msg->list_head));
list_add_tail(&msg->list_head, &con->out_queue);
@@ -3038,16 +3036,15 @@ void ceph_msg_revoke(struct ceph_msg *msg)
{
struct ceph_connection *con = msg->con;
- if (!con)
+ if (!con) {
+ dout("%s msg %p null con\n", __func__, msg);
return; /* Message not in our possession */
+ }
mutex_lock(&con->mutex);
if (!list_empty(&msg->list_head)) {
dout("%s %p msg %p - was on queue\n", __func__, con, msg);
list_del_init(&msg->list_head);
- BUG_ON(msg->con == NULL);
- msg->con->ops->put(msg->con);
- msg->con = NULL;
msg->hdr.seq = 0;
ceph_msg_put(msg);
@@ -3071,16 +3068,13 @@ void ceph_msg_revoke(struct ceph_msg *msg)
*/
void ceph_msg_revoke_incoming(struct ceph_msg *msg)
{
- struct ceph_connection *con;
+ struct ceph_connection *con = msg->con;
- BUG_ON(msg == NULL);
- if (!msg->con) {
+ if (!con) {
dout("%s msg %p null con\n", __func__, msg);
-
return; /* Message not in our possession */
}
- con = msg->con;
mutex_lock(&con->mutex);
if (con->in_msg == msg) {
unsigned int front_len = le32_to_cpu(con->in_hdr.front_len);
@@ -3326,9 +3320,8 @@ static int ceph_con_in_msg_alloc(struct ceph_connection *con, int *skip)
}
if (msg) {
BUG_ON(*skip);
+ msg_con_set(msg, con);
con->in_msg = msg;
- con->in_msg->con = con->ops->get(con);
- BUG_ON(con->in_msg->con == NULL);
} else {
/*
* Null message pointer means either we should skip
@@ -3375,6 +3368,8 @@ static void ceph_msg_release(struct kref *kref)
dout("%s %p\n", __func__, m);
WARN_ON(!list_empty(&m->list_head));
+ msg_con_set(m, NULL);
+
/* drop middle, data, if any */
if (m->middle) {
ceph_buffer_put(m->middle);
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 118e4ce37ecc..f8f235930d88 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -2850,9 +2850,6 @@ static struct ceph_msg *get_reply(struct ceph_connection *con,
goto out;
}
- if (req->r_reply->con)
- dout("%s revoking msg %p from old con %p\n", __func__,
- req->r_reply, req->r_reply->con);
ceph_msg_revoke_incoming(req->r_reply);
if (front_len > req->r_reply->front_alloc_len) {
--
2.4.3
--
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