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 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 --- fs/smb/server/auth.c | 4 ++-- fs/smb/server/mgmt/user_session.c | 14 ++++++++------ fs/smb/server/smb2pdu.c | 7 ++++--- 3 files changed, 14 insertions(+), 11 deletions(-)
--- a/fs/smb/server/auth.c +++ b/fs/smb/server/auth.c @@ -1010,9 +1010,9 @@ static int ksmbd_get_encryption_key(stru
ses_enc_key = enc ? sess->smb3encryptionkey : sess->smb3decryptionkey; - if (enc) - ksmbd_user_session_get(sess); memcpy(key, ses_enc_key, SMB3_ENC_DEC_KEY_SIZE); + if (!enc) + ksmbd_user_session_put(sess);
return 0; } --- a/fs/smb/server/mgmt/user_session.c +++ b/fs/smb/server/mgmt/user_session.c @@ -180,7 +180,7 @@ static void ksmbd_expire_session(struct down_write(&sessions_table_lock); down_write(&conn->session_lock); xa_for_each(&conn->sessions, id, sess) { - if (atomic_read(&sess->refcnt) == 0 && + if (atomic_read(&sess->refcnt) <= 1 && (sess->state != SMB2_SESSION_VALID || time_after(jiffies, sess->last_active + SMB2_SESSION_TIMEOUT))) { @@ -232,7 +232,8 @@ void ksmbd_sessions_deregister(struct ks down_write(&conn->session_lock); xa_erase(&conn->sessions, sess->id); up_write(&conn->session_lock); - ksmbd_session_destroy(sess); + if (atomic_dec_and_test(&sess->refcnt)) + ksmbd_session_destroy(sess); } } } @@ -251,7 +252,8 @@ void ksmbd_sessions_deregister(struct ks if (xa_empty(&sess->ksmbd_chann_list)) { xa_erase(&conn->sessions, sess->id); hash_del(&sess->hlist); - ksmbd_session_destroy(sess); + if (atomic_dec_and_test(&sess->refcnt)) + ksmbd_session_destroy(sess); } } up_write(&conn->session_lock); @@ -327,8 +329,8 @@ void ksmbd_user_session_put(struct ksmbd
if (atomic_read(&sess->refcnt) <= 0) WARN_ON(1); - else - atomic_dec(&sess->refcnt); + else if (atomic_dec_and_test(&sess->refcnt)) + ksmbd_session_destroy(sess); }
struct preauth_session *ksmbd_preauth_session_alloc(struct ksmbd_conn *conn, @@ -399,7 +401,7 @@ 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); + atomic_set(&sess->refcnt, 2);
ret = __init_smb2_session(sess); if (ret) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -2242,13 +2242,14 @@ int smb2_session_logoff(struct ksmbd_wor return -ENOENT; }
- 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; + if (sess->user) { + ksmbd_free_user(sess->user); + sess->user = NULL; + } ksmbd_all_conn_set_status(sess_id, KSMBD_SESS_NEED_NEGOTIATE);
rsp->StructureSize = cpu_to_le16(4);