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 >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 59c6dcc5dd9dafe764ca0d40525933b2be69b059
• Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a
• Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 517404e157395d0f8da125ca956c566895dfcd06
• Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 4722d06b2907585074252061b1024a696c1cfc23
• Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 23a0be6a84a38ac169eeab49017934e8e27c65f0
• Linux 676392184785ace61e939831e7ca44a03d438c3b
• Linux ef572ffa8eb44111eed2925fbb2adca78bdcbf61
• Linux 2ba03cecb12ac7ac9e0170e251543c56832d9959
• Linux >= 5.15.145 < 5.16
• Linux >= 6.1.40 < 6.2
• Linux >= 6.4.5 < 6.5
• Linux 6.5

Remediation

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