6.1-stable review patch. If anyone has any objections, please let me know.
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From: Namjae Jeon linkinjeon@kernel.org
commit 7aa8804c0b67b3cb263a472d17f2cb50d7f1a930 upstream.
There is racy issue between smb2 session log off and smb2 session setup. It will cause user-after-free from session log off. This add session_lock when setting SMB2_SESSION_EXPIRED and referece count to session struct not to free session while it is being used.
Cc: stable@vger.kernel.org # v5.15+ Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-25282 Signed-off-by: Namjae Jeon linkinjeon@kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/smb/server/mgmt/user_session.c | 26 +++++++++++++++++++++----- fs/smb/server/mgmt/user_session.h | 4 ++++ fs/smb/server/server.c | 2 ++ fs/smb/server/smb2pdu.c | 8 +++++++- 4 files changed, 34 insertions(+), 6 deletions(-)
--- a/fs/smb/server/mgmt/user_session.c +++ b/fs/smb/server/mgmt/user_session.c @@ -176,9 +176,10 @@ static void ksmbd_expire_session(struct
down_write(&conn->session_lock); xa_for_each(&conn->sessions, id, sess) { - if (sess->state != SMB2_SESSION_VALID || - time_after(jiffies, - sess->last_active + SMB2_SESSION_TIMEOUT)) { + if (atomic_read(&sess->refcnt) == 0 && + (sess->state != SMB2_SESSION_VALID || + time_after(jiffies, + sess->last_active + SMB2_SESSION_TIMEOUT))) { xa_erase(&conn->sessions, sess->id); hash_del(&sess->hlist); ksmbd_session_destroy(sess); @@ -268,8 +269,6 @@ struct ksmbd_session *ksmbd_session_look
down_read(&sessions_table_lock); sess = __session_lookup(id); - if (sess) - sess->last_active = jiffies; up_read(&sessions_table_lock);
return sess; @@ -288,6 +287,22 @@ struct ksmbd_session *ksmbd_session_look return sess; }
+void ksmbd_user_session_get(struct ksmbd_session *sess) +{ + atomic_inc(&sess->refcnt); +} + +void ksmbd_user_session_put(struct ksmbd_session *sess) +{ + if (!sess) + return; + + if (atomic_read(&sess->refcnt) <= 0) + WARN_ON(1); + else + atomic_dec(&sess->refcnt); +} + struct preauth_session *ksmbd_preauth_session_alloc(struct ksmbd_conn *conn, u64 sess_id) { @@ -356,6 +371,7 @@ static struct ksmbd_session *__session_c xa_init(&sess->rpc_handle_list); sess->sequence_number = 1; rwlock_init(&sess->tree_conns_lock); + atomic_set(&sess->refcnt, 1);
ret = __init_smb2_session(sess); if (ret) --- a/fs/smb/server/mgmt/user_session.h +++ b/fs/smb/server/mgmt/user_session.h @@ -61,6 +61,8 @@ struct ksmbd_session { struct ksmbd_file_table file_table; unsigned long last_active; rwlock_t tree_conns_lock; + + atomic_t refcnt; };
static inline int test_session_flag(struct ksmbd_session *sess, int bit) @@ -101,4 +103,6 @@ void ksmbd_release_tree_conn_id(struct k int ksmbd_session_rpc_open(struct ksmbd_session *sess, char *rpc_name); void ksmbd_session_rpc_close(struct ksmbd_session *sess, int id); int ksmbd_session_rpc_method(struct ksmbd_session *sess, int id); +void ksmbd_user_session_get(struct ksmbd_session *sess); +void ksmbd_user_session_put(struct ksmbd_session *sess); #endif /* __USER_SESSION_MANAGEMENT_H__ */ --- a/fs/smb/server/server.c +++ b/fs/smb/server/server.c @@ -238,6 +238,8 @@ static void __handle_ksmbd_work(struct k } while (is_chained == true);
send: + if (work->sess) + ksmbd_user_session_put(work->sess); if (work->tcon) ksmbd_tree_connect_put(work->tcon); smb3_preauth_hash_rsp(work); --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -604,8 +604,10 @@ int smb2_check_user_session(struct ksmbd
/* Check for validity of user session */ work->sess = ksmbd_session_lookup_all(conn, sess_id); - if (work->sess) + if (work->sess) { + ksmbd_user_session_get(work->sess); return 1; + } ksmbd_debug(SMB, "Invalid user session, Uid %llu\n", sess_id); return -ENOENT; } @@ -1759,6 +1761,7 @@ int smb2_sess_setup(struct ksmbd_work *w }
conn->binding = true; + ksmbd_user_session_get(sess); } else if ((conn->dialect < SMB30_PROT_ID || server_conf.flags & KSMBD_GLOBAL_FLAG_SMB3_MULTICHANNEL) && (req->Flags & SMB2_SESSION_REQ_FLAG_BINDING)) { @@ -1785,6 +1788,7 @@ int smb2_sess_setup(struct ksmbd_work *w }
conn->binding = false; + ksmbd_user_session_get(sess); } work->sess = sess;
@@ -2240,7 +2244,9 @@ int smb2_session_logoff(struct ksmbd_wor }
ksmbd_destroy_file_table(&sess->file_table); + down_write(&conn->session_lock); sess->state = SMB2_SESSION_EXPIRED; + up_write(&conn->session_lock);
ksmbd_free_user(sess->user); sess->user = NULL;