tpm: fix off-by-four bounds check in tpm2_get_random()

Overview

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

tpm: fix off-by-four bounds check in tpm2_get_random()

When the response carries the TPM2_ST_SESSIONS tag, tpm2_get_random() skips the 4-byte parameter size field before locating the random data, but the bounds check still validates the response length against TPM_HEADER_SIZE. A truncated response can pass the check and make memcpy() read up to 4 bytes past the response end, so stale buffer contents end up in the caller's random bytes.

Fix this by checking the response length against 'offset', which already includes the skipped parameter size field.

Affected

• Linux >= 1b6d7f9eb150305dcb0da4f7101a8d30dcdf0497 < be54101992c2c5218be0e0a87827ccc96e3089af
• Linux >= 1b6d7f9eb150305dcb0da4f7101a8d30dcdf0497 < e30a2406408d2df6d9cd48c2e59e913cf266a05a
• Linux >= 1b6d7f9eb150305dcb0da4f7101a8d30dcdf0497 < 42bb6216b861e892512128219ff23010d656ba14
• Linux >= 1b6d7f9eb150305dcb0da4f7101a8d30dcdf0497 < 9b522400bf5c082feb9a0037a053ea822a2c7e4d
• Linux 6.10

Remediation

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