CVE-2026-53038

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

ima_fs: Correctly create securityfs files for unsupported hash algos

ima_tpm_chip->allocated_banks[i].crypto_id is initialized to

HASH_ALGO__LAST if the TPM algorithm is not supported. However there

are places relying on the algorithm to be valid because it is accessed

by hash_algo_name[].

On 6.12.40 I observe the following read out-of-bounds in hash_algo_name:

==================================================================

BUG: KASAN: global-out-of-bounds in create_securityfs_measurement_lists+0x396/0x440

Read of size 8 at addr ffffffff83e18138 by task swapper/0/1

CPU: 4 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.40 #3

Call Trace:

<TASK>

dump_stack_lvl+0x61/0x90

print_report+0xc4/0x580

? kasan_addr_to_slab+0x26/0x80

? create_securityfs_measurement_lists+0x396/0x440

kasan_report+0xc2/0x100

? create_securityfs_measurement_lists+0x396/0x440

create_securityfs_measurement_lists+0x396/0x440

ima_fs_init+0xa3/0x300

ima_init+0x7d/0xd0

init_ima+0x28/0x100

do_one_initcall+0xa6/0x3e0

kernel_init_freeable+0x455/0x740

kernel_init+0x24/0x1d0

ret_from_fork+0x38/0x80

ret_from_fork_asm+0x11/0x20

</TASK>

The buggy address belongs to the variable:

hash_algo_name+0xb8/0x420

Memory state around the buggy address:

ffffffff83e18000: 00 01 f9 f9 f9 f9 f9 f9 00 01 f9 f9 f9 f9 f9 f9

ffffffff83e18080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

>ffffffff83e18100: 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 00 05 f9 f9

^

ffffffff83e18180: f9 f9 f9 f9 00 00 00 00 00 00 00 04 f9 f9 f9 f9

ffffffff83e18200: 00 00 00 00 00 00 00 00 04 f9 f9 f9 f9 f9 f9 f9

==================================================================

Seems like the TPM chip supports sha3_256, which isn't yet in

tpm_algorithms:

tpm tpm0: TPM with unsupported bank algorithm 0x0027

That's TPM_ALG_SHA3_256 == 0x0027 from "Trusted Platform Module 2.0

Library Part 2: Structures", page 51 [1].

See also the related U-Boot algorithms update [2].

Thus solve the problem by creating a file name with "_tpm_alg_<ID>"

postfix if the crypto algorithm isn't initialized.

This is how it looks on the test machine (patch ported to v6.12 release):

# ls -1 /sys/kernel/security/ima/

ascii_runtime_measurements

ascii_runtime_measurements_tpm_alg_27

ascii_runtime_measurements_sha1

ascii_runtime_measurements_sha256

binary_runtime_measurements

binary_runtime_measurements_tpm_alg_27

binary_runtime_measurements_sha1

binary_runtime_measurements_sha256

policy

runtime_measurements_count

violations

[1]: https://trustedcomputinggroup.org/wp-content/uploads/Trusted-Platform-Module-2.0-Library-Part-2-Version-184_pub.pdf

[2]: https://lists.denx.de/pipermail/u-boot/2024-July/558835.html