ksmbd: fix heap out-of-bounds write in krb5_authenticate()

Overview

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix heap out-of-bounds write in krb5_authenticate()

In krb5_authenticate(), out_len is calculated to determine available headroom in response_buf for the incoming Kerberos AP-REP token. However, when SMB2_SESSION_SETUP is processed as a non-first element of a compounded SMB2 request, the calculation omits work->next_smb2_rsp_hdr_off.

This causes out_len to overstate remaining buffer headroom by the cumulative size of prior responses in the compound chain. Consequently, the length check in ksmbd_krb5_authenticate() (*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy() to write the AP-REP blob past the end of response_buf into adjacent kernel heap memory.

Fix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len, ensuring it accurately reflects physical remaining buffer space.

Affected

• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 59c6dcc5dd9dafe764ca0d40525933b2be69b059
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 517404e157395d0f8da125ca956c566895dfcd06
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4722d06b2907585074252061b1024a696c1cfc23
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 23a0be6a84a38ac169eeab49017934e8e27c65f0
• Linux < 6.6.160
• Linux < 6.12.114
• Linux < 6.18.58
• Linux < 7.2.12
• Linux (all versions)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.