57 lines
1.8 KiB
Diff
57 lines
1.8 KiB
Diff
From 6e367a428b98393cd5d0ab993983ba40dc748ca5 Mon Sep 17 00:00:00 2001
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From: Sean Heelan <seanheelan@gmail.com>
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Date: Sat, 19 Apr 2025 19:59:28 +0100
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Subject: ksmbd: fix use-after-free in kerberos authentication
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Setting sess->user = NULL was introduced to fix the dangling pointer
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created by ksmbd_free_user. However, it is possible another thread could
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be operating on the session and make use of sess->user after it has been
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passed to ksmbd_free_user but before sess->user is set to NULL.
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Cc: stable@vger.kernel.org
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Signed-off-by: Sean Heelan <seanheelan@gmail.com>
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Acked-by: Namjae Jeon <linkinjeon@kernel.org>
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Signed-off-by: Steve French <stfrench@microsoft.com>
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---
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fs/smb/server/auth.c | 14 +++++++++++++-
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fs/smb/server/smb2pdu.c | 5 -----
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2 files changed, 13 insertions(+), 6 deletions(-)
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--- a/fs/smb/server/auth.c
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+++ b/fs/smb/server/auth.c
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@@ -550,7 +550,19 @@ int ksmbd_krb5_authenticate(struct ksmbd
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retval = -ENOMEM;
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goto out;
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}
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- sess->user = user;
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+
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+ if (!sess->user) {
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+ /* First successful authentication */
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+ sess->user = user;
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+ } else {
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+ if (!ksmbd_compare_user(sess->user, user)) {
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+ ksmbd_debug(AUTH, "different user tried to reuse session\n");
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+ retval = -EPERM;
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+ ksmbd_free_user(user);
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+ goto out;
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+ }
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+ ksmbd_free_user(user);
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+ }
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memcpy(sess->sess_key, resp->payload, resp->session_key_len);
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memcpy(out_blob, resp->payload + resp->session_key_len,
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--- a/fs/smb/server/smb2pdu.c
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+++ b/fs/smb/server/smb2pdu.c
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@@ -1602,11 +1602,6 @@ static int krb5_authenticate(struct ksmb
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if (prev_sess_id && prev_sess_id != sess->id)
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destroy_previous_session(conn, sess->user, prev_sess_id);
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- if (sess->state == SMB2_SESSION_VALID) {
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- ksmbd_free_user(sess->user);
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- sess->user = NULL;
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- }
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-
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retval = ksmbd_krb5_authenticate(sess, in_blob, in_len,
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out_blob, &out_len);
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if (retval) {
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