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ksmbd: fix session use-after-free in multichannel connection

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commit fa4cdb8cbca7d6cb6aa13e4d8d83d1103f6345db upstream.

There is a race condition between session setup and
ksmbd_sessions_deregister. The session can be freed before the connection
is added to channel list of session.
This patch check reference count of session before freeing it.

Cc: stable@vger.kernel.org
Reported-by: Sean Heelan <seanheelan@gmail.com>
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>
This commit is contained in:
Namjae Jeon 2025-03-27 21:22:51 +09:00 committed by Greg Kroah-Hartman
parent f0eb3f5751
commit 596407adb9
3 changed files with 14 additions and 11 deletions

4
fs/smb/server/auth.c

@ -1010,9 +1010,9 @@ static int ksmbd_get_encryption_key(struct ksmbd_work *work, __u64 ses_id,
ses_enc_key = enc ? sess->smb3encryptionkey : ses_enc_key = enc ? sess->smb3encryptionkey :
sess->smb3decryptionkey; sess->smb3decryptionkey;
if (enc)
ksmbd_user_session_get(sess);
memcpy(key, ses_enc_key, SMB3_ENC_DEC_KEY_SIZE); memcpy(key, ses_enc_key, SMB3_ENC_DEC_KEY_SIZE);
if (!enc)
ksmbd_user_session_put(sess);
return 0; return 0;
} }

10
fs/smb/server/mgmt/user_session.c

@ -180,7 +180,7 @@ static void ksmbd_expire_session(struct ksmbd_conn *conn)
down_write(&sessions_table_lock); down_write(&sessions_table_lock);
down_write(&conn->session_lock); down_write(&conn->session_lock);
xa_for_each(&conn->sessions, id, sess) { xa_for_each(&conn->sessions, id, sess) {
if (atomic_read(&sess->refcnt) == 0 && if (atomic_read(&sess->refcnt) <= 1 &&
(sess->state != SMB2_SESSION_VALID || (sess->state != SMB2_SESSION_VALID ||
time_after(jiffies, time_after(jiffies,
sess->last_active + SMB2_SESSION_TIMEOUT))) { sess->last_active + SMB2_SESSION_TIMEOUT))) {
@ -232,6 +232,7 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn)
down_write(&conn->session_lock); down_write(&conn->session_lock);
xa_erase(&conn->sessions, sess->id); xa_erase(&conn->sessions, sess->id);
up_write(&conn->session_lock); up_write(&conn->session_lock);
if (atomic_dec_and_test(&sess->refcnt))
ksmbd_session_destroy(sess); ksmbd_session_destroy(sess);
} }
} }
@ -251,6 +252,7 @@ void ksmbd_sessions_deregister(struct ksmbd_conn *conn)
if (xa_empty(&sess->ksmbd_chann_list)) { if (xa_empty(&sess->ksmbd_chann_list)) {
xa_erase(&conn->sessions, sess->id); xa_erase(&conn->sessions, sess->id);
hash_del(&sess->hlist); hash_del(&sess->hlist);
if (atomic_dec_and_test(&sess->refcnt))
ksmbd_session_destroy(sess); ksmbd_session_destroy(sess);
} }
} }
@ -327,8 +329,8 @@ void ksmbd_user_session_put(struct ksmbd_session *sess)
if (atomic_read(&sess->refcnt) <= 0) if (atomic_read(&sess->refcnt) <= 0)
WARN_ON(1); WARN_ON(1);
else else if (atomic_dec_and_test(&sess->refcnt))
atomic_dec(&sess->refcnt); ksmbd_session_destroy(sess);
} }
struct preauth_session *ksmbd_preauth_session_alloc(struct ksmbd_conn *conn, struct preauth_session *ksmbd_preauth_session_alloc(struct ksmbd_conn *conn,
@ -399,7 +401,7 @@ static struct ksmbd_session *__session_create(int protocol)
xa_init(&sess->rpc_handle_list); xa_init(&sess->rpc_handle_list);
sess->sequence_number = 1; sess->sequence_number = 1;
rwlock_init(&sess->tree_conns_lock); rwlock_init(&sess->tree_conns_lock);
atomic_set(&sess->refcnt, 1); atomic_set(&sess->refcnt, 2);
ret = __init_smb2_session(sess); ret = __init_smb2_session(sess);
if (ret) if (ret)

3
fs/smb/server/smb2pdu.c

@ -2242,13 +2242,14 @@ int smb2_session_logoff(struct ksmbd_work *work)
return -ENOENT; return -ENOENT;
} }
ksmbd_destroy_file_table(&sess->file_table);
down_write(&conn->session_lock); down_write(&conn->session_lock);
sess->state = SMB2_SESSION_EXPIRED; sess->state = SMB2_SESSION_EXPIRED;
up_write(&conn->session_lock); up_write(&conn->session_lock);
if (sess->user) {
ksmbd_free_user(sess->user); ksmbd_free_user(sess->user);
sess->user = NULL; sess->user = NULL;
}
ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_NEGOTIATE); ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_NEGOTIATE);
rsp->StructureSize = cpu_to_le16(4); rsp->StructureSize = cpu_to_le16(4);