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ksmbd: fix null pointer dereference in destroy_previous_session

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If client set ->PreviousSessionId on kerberos session setup stage,
NULL pointer dereference error will happen. Since sess->user is not
set yet, It can pass the user argument as NULL to destroy_previous_session.
sess->user will be set in ksmbd_krb5_authenticate(). So this patch move
calling destroy_previous_session() after ksmbd_krb5_authenticate().

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-27391
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Namjae Jeon
2025-06-13 10:12:43 +09:00
committed by Steve French
parent a89f5fae99
commit 7ac5b66aca
1 changed files with 6 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/smb/server/smb2pdu.c
+6 -5
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@@ -1607,17 +1607,18 @@ static int krb5_authenticate(struct ksmbd_work *work,
out_len = work->response_sz -
(le16_to_cpu(rsp->SecurityBufferOffset) + 4);
/* Check previous session */
prev_sess_id = le64_to_cpu(req->PreviousSessionId);
if (prev_sess_id && prev_sess_id != sess->id)
destroy_previous_session(conn, sess->user, prev_sess_id);
retval = ksmbd_krb5_authenticate(sess, in_blob, in_len,
out_blob, &out_len);
if (retval) {
ksmbd_debug(SMB, "krb5 authentication failed\n");
return -EINVAL;
}
/* Check previous session */
prev_sess_id = le64_to_cpu(req->PreviousSessionId);
if (prev_sess_id && prev_sess_id != sess->id)
destroy_previous_session(conn, sess->user, prev_sess_id);
rsp->SecurityBufferLength = cpu_to_le16(out_len);
if ((conn->sign || server_conf.enforced_signing) ||