The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 7aa8804c0b67b3cb263a472d17f2cb50d7f1a930 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024101744-fence-valiant-9382@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7aa8804c0b67b3cb263a472d17f2cb50d7f1a930 Mon Sep 17 00:00:00 2001 From: Namjae Jeon linkinjeon@kernel.org Date: Tue, 8 Oct 2024 22:42:57 +0900 Subject: [PATCH] ksmbd: fix user-after-free from session log off

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

diff --git a/fs/smb/server/mgmt/user_session.c b/fs/smb/server/mgmt/user_session.c index 99416ce9f501..1e4624e9d434 100644 --- a/fs/smb/server/mgmt/user_session.c +++ b/fs/smb/server/mgmt/user_session.c @@ -177,9 +177,10 @@ static void ksmbd_expire_session(struct ksmbd_conn *conn)

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); @@ -269,8 +270,6 @@ struct ksmbd_session *ksmbd_session_lookup_slowpath(unsigned long long id)

down_read(&sessions_table_lock); sess = __session_lookup(id); - if (sess) - sess->last_active = jiffies; up_read(&sessions_table_lock);

return sess; @@ -289,6 +288,22 @@ struct ksmbd_session *ksmbd_session_lookup_all(struct ksmbd_conn *conn, 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) { @@ -393,6 +408,7 @@ static struct ksmbd_session *__session_create(int protocol) 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) diff --git a/fs/smb/server/mgmt/user_session.h b/fs/smb/server/mgmt/user_session.h index dc9fded2cd43..c1c4b20bd5c6 100644 --- 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) @@ -104,4 +106,6 @@ void ksmbd_release_tree_conn_id(struct ksmbd_session *sess, int id); 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__ */ diff --git a/fs/smb/server/server.c b/fs/smb/server/server.c index 231d2d224656..9670c97f14b3 100644 --- a/fs/smb/server/server.c +++ b/fs/smb/server/server.c @@ -238,6 +238,8 @@ static void __handle_ksmbd_work(struct ksmbd_work *work, } 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); diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 797b0f24097b..599118aed205 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -605,8 +605,10 @@ int smb2_check_user_session(struct ksmbd_work *work)

/* 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; } @@ -1740,6 +1742,7 @@ int smb2_sess_setup(struct ksmbd_work *work) }

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)) { @@ -1766,6 +1769,7 @@ int smb2_sess_setup(struct ksmbd_work *work) }

conn->binding = false; + ksmbd_user_session_get(sess); } work->sess = sess;

@@ -2228,7 +2232,9 @@ int smb2_session_logoff(struct ksmbd_work *work) }

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;