This is a note to let you know that I've just added the patch titled
ksmbd: fix race condition between tree conn lookup and disconnect
to the 6.1-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:
ksmbd-fix-race-condition-between-tree-conn-lookup-an.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 67710341be33231c229f95062e6fc7dc194e81cb
Author: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Date: Sun Dec 31 16:13:07 2023 +0900
ksmbd: fix race condition between tree conn lookup and disconnect
[ Upstream commit 33b235a6e6ebe0f05f3586a71e8d281d00f71e2e ]
if thread A in smb2_write is using work-tcon, other thread B use
smb2_tree_disconnect free the tcon, then thread A will use free'd tcon.
Time
+
Thread A | Thread A
smb2_write | smb2_tree_disconnect
|
|
| kfree(tree_conn)
|
// UAF! |
work->tcon->share_conf |
+
This patch add state, reference count and lock for tree conn to fix race
condition issue.
Reported-by: luosili <rootlab@xxxxxxxxxx>
Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/smb/server/mgmt/tree_connect.c b/fs/smb/server/mgmt/tree_connect.c
index 408cddf2f094a..d2c81a8a11dda 100644
--- a/fs/smb/server/mgmt/tree_connect.c
+++ b/fs/smb/server/mgmt/tree_connect.c
@@ -73,7 +73,10 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
tree_conn->user = sess->user;
tree_conn->share_conf = sc;
+ tree_conn->t_state = TREE_NEW;
status.tree_conn = tree_conn;
+ atomic_set(&tree_conn->refcount, 1);
+ init_waitqueue_head(&tree_conn->refcount_q);
ret = xa_err(xa_store(&sess->tree_conns, tree_conn->id, tree_conn,
GFP_KERNEL));
@@ -93,14 +96,33 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
return status;
}
+void ksmbd_tree_connect_put(struct ksmbd_tree_connect *tcon)
+{
+ /*
+ * Checking waitqueue to releasing tree connect on
+ * tree disconnect. waitqueue_active is safe because it
+ * uses atomic operation for condition.
+ */
+ if (!atomic_dec_return(&tcon->refcount) &&
+ waitqueue_active(&tcon->refcount_q))
+ wake_up(&tcon->refcount_q);
+}
+
int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
struct ksmbd_tree_connect *tree_conn)
{
int ret;
+ write_lock(&sess->tree_conns_lock);
+ xa_erase(&sess->tree_conns, tree_conn->id);
+ write_unlock(&sess->tree_conns_lock);
+
+ if (!atomic_dec_and_test(&tree_conn->refcount))
+ wait_event(tree_conn->refcount_q,
+ atomic_read(&tree_conn->refcount) == 0);
+
ret = ksmbd_ipc_tree_disconnect_request(sess->id, tree_conn->id);
ksmbd_release_tree_conn_id(sess, tree_conn->id);
- xa_erase(&sess->tree_conns, tree_conn->id);
ksmbd_share_config_put(tree_conn->share_conf);
kfree(tree_conn);
return ret;
@@ -111,11 +133,15 @@ struct ksmbd_tree_connect *ksmbd_tree_conn_lookup(struct ksmbd_session *sess,
{
struct ksmbd_tree_connect *tcon;
+ read_lock(&sess->tree_conns_lock);
tcon = xa_load(&sess->tree_conns, id);
if (tcon) {
- if (test_bit(TREE_CONN_EXPIRE, &tcon->status))
+ if (tcon->t_state != TREE_CONNECTED)
+ tcon = NULL;
+ else if (!atomic_inc_not_zero(&tcon->refcount))
tcon = NULL;
}
+ read_unlock(&sess->tree_conns_lock);
return tcon;
}
@@ -129,8 +155,18 @@ int ksmbd_tree_conn_session_logoff(struct ksmbd_session *sess)
if (!sess)
return -EINVAL;
- xa_for_each(&sess->tree_conns, id, tc)
+ xa_for_each(&sess->tree_conns, id, tc) {
+ write_lock(&sess->tree_conns_lock);
+ if (tc->t_state == TREE_DISCONNECTED) {
+ write_unlock(&sess->tree_conns_lock);
+ ret = -ENOENT;
+ continue;
+ }
+ tc->t_state = TREE_DISCONNECTED;
+ write_unlock(&sess->tree_conns_lock);
+
ret |= ksmbd_tree_conn_disconnect(sess, tc);
+ }
xa_destroy(&sess->tree_conns);
return ret;
}
diff --git a/fs/smb/server/mgmt/tree_connect.h b/fs/smb/server/mgmt/tree_connect.h
index 562d647ad9fad..6377a70b811c8 100644
--- a/fs/smb/server/mgmt/tree_connect.h
+++ b/fs/smb/server/mgmt/tree_connect.h
@@ -14,7 +14,11 @@ struct ksmbd_share_config;
struct ksmbd_user;
struct ksmbd_conn;
-#define TREE_CONN_EXPIRE 1
+enum {
+ TREE_NEW = 0,
+ TREE_CONNECTED,
+ TREE_DISCONNECTED
+};
struct ksmbd_tree_connect {
int id;
@@ -27,7 +31,9 @@ struct ksmbd_tree_connect {
int maximal_access;
bool posix_extensions;
- unsigned long status;
+ atomic_t refcount;
+ wait_queue_head_t refcount_q;
+ unsigned int t_state;
};
struct ksmbd_tree_conn_status {
@@ -46,6 +52,7 @@ struct ksmbd_session;
struct ksmbd_tree_conn_status
ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
const char *share_name);
+void ksmbd_tree_connect_put(struct ksmbd_tree_connect *tcon);
int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
struct ksmbd_tree_connect *tree_conn);
diff --git a/fs/smb/server/mgmt/user_session.c b/fs/smb/server/mgmt/user_session.c
index b8be14a96cf66..15f68ee050894 100644
--- a/fs/smb/server/mgmt/user_session.c
+++ b/fs/smb/server/mgmt/user_session.c
@@ -355,6 +355,7 @@ static struct ksmbd_session *__session_create(int protocol)
xa_init(&sess->ksmbd_chann_list);
xa_init(&sess->rpc_handle_list);
sess->sequence_number = 1;
+ rwlock_init(&sess->tree_conns_lock);
ret = __init_smb2_session(sess);
if (ret)
diff --git a/fs/smb/server/mgmt/user_session.h b/fs/smb/server/mgmt/user_session.h
index f99d475b28db4..63cb08fffde84 100644
--- a/fs/smb/server/mgmt/user_session.h
+++ b/fs/smb/server/mgmt/user_session.h
@@ -60,6 +60,7 @@ struct ksmbd_session {
struct ksmbd_file_table file_table;
unsigned long last_active;
+ rwlock_t tree_conns_lock;
};
static inline int test_session_flag(struct ksmbd_session *sess, int bit)
diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c
index 633383e55723c..11b201e6ee44b 100644
--- a/fs/smb/server/server.c
+++ b/fs/smb/server/server.c
@@ -241,6 +241,8 @@ static void __handle_ksmbd_work(struct ksmbd_work *work,
} while (is_chained == true);
send:
+ if (work->tcon)
+ ksmbd_tree_connect_put(work->tcon);
smb3_preauth_hash_rsp(work);
if (work->sess && work->sess->enc && work->encrypted &&
conn->ops->encrypt_resp) {
diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index a76529512acfb..aad08866746c8 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -1993,6 +1993,9 @@ int smb2_tree_connect(struct ksmbd_work *work)
if (conn->posix_ext_supported)
status.tree_conn->posix_extensions = true;
+ write_lock(&sess->tree_conns_lock);
+ status.tree_conn->t_state = TREE_CONNECTED;
+ write_unlock(&sess->tree_conns_lock);
rsp->StructureSize = cpu_to_le16(16);
out_err1:
rsp->Capabilities = 0;
@@ -2122,27 +2125,50 @@ int smb2_tree_disconnect(struct ksmbd_work *work)
ksmbd_debug(SMB, "request\n");
+ if (!tcon) {
+ ksmbd_debug(SMB, "Invalid tid %d\n", req->hdr.Id.SyncId.TreeId);
+
+ rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
+ err = -ENOENT;
+ goto err_out;
+ }
+
+ ksmbd_close_tree_conn_fds(work);
+
+ write_lock(&sess->tree_conns_lock);
+ if (tcon->t_state == TREE_DISCONNECTED) {
+ write_unlock(&sess->tree_conns_lock);
+ rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
+ err = -ENOENT;
+ goto err_out;
+ }
+
+ WARN_ON_ONCE(atomic_dec_and_test(&tcon->refcount));
+ tcon->t_state = TREE_DISCONNECTED;
+ write_unlock(&sess->tree_conns_lock);
+
+ err = ksmbd_tree_conn_disconnect(sess, tcon);
+ if (err) {
+ rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
+ goto err_out;
+ }
+
+ work->tcon = NULL;
+
rsp->StructureSize = cpu_to_le16(4);
err = ksmbd_iov_pin_rsp(work, rsp,
sizeof(struct smb2_tree_disconnect_rsp));
if (err) {
rsp->hdr.Status = STATUS_INSUFFICIENT_RESOURCES;
- smb2_set_err_rsp(work);
- return err;
+ goto err_out;
}
- if (!tcon || test_and_set_bit(TREE_CONN_EXPIRE, &tcon->status)) {
- ksmbd_debug(SMB, "Invalid tid %d\n", req->hdr.Id.SyncId.TreeId);
+ return 0;
- rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;
- smb2_set_err_rsp(work);
- return -ENOENT;
- }
+err_out:
+ smb2_set_err_rsp(work);
+ return err;
- ksmbd_close_tree_conn_fds(work);
- ksmbd_tree_conn_disconnect(sess, tcon);
- work->tcon = NULL;
- return 0;
}
/**
