cipso: adjust cached option offsets when removing CIPSO

Overview

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

cipso: adjust cached option offsets when removing CIPSO

cipso_v4_skbuff_delattr() removes the CIPSO bytes but does not adjust cached offsets for options that follow them.

For example, with a valid 10-byte CIPSO option followed by a seven-byte RR option, parsing records rr at offset 30. Removing CIPSO moves RR to offset 20, while the cached offset remains 30. Consumers such as ip_forward_options() and __ip_options_echo() then access the wrong bytes; the latter may interpret packet data as the option length and copy it into fixed-size option storage.

Mirror cipso_v4_delopt() and subtract cipso_len from the srr, rr, ts and router_alert offsets when they follow CIPSO. cipso_len is the distance the first memmove() shifts those options. The later header move and network-header reset relocate the bytes and their offset base together.

Affected

• Linux >= 89aa3619d141d6cfb6040a561aebb6d99d3e2285 < b965977126a90e01825814c859ba4788691eddd3
• Linux >= 89aa3619d141d6cfb6040a561aebb6d99d3e2285 < 2200fe1d6148b78e1b8f00f4b2bd47760015077f
• Linux >= 89aa3619d141d6cfb6040a561aebb6d99d3e2285 < 6e49d611a9cfbaac927b8fa80ebd4f6b1f37ada0
• Linux >= 89aa3619d141d6cfb6040a561aebb6d99d3e2285 < 6d25ffca055a77787c21a36b66c253f76239411b
• Linux 6.10

Remediation

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