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d7bd8cf0b3
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
Fixes: 9fa8e76250 ("ima: add crypto agility support for template-hash algorithm")
Signed-off-by: Dmitry Safonov <dima@arista.com>
Cc: Enrico Bravi <enrico.bravi@polito.it>
Cc: Silvia Sisinni <silvia.sisinni@polito.it>
Cc: Roberto Sassu <roberto.sassu@huawei.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Tested-by: Roberto Sassu <roberto.sassu@huawei.com>
Link: https://github.com/linux-integrity/linux/issues/14
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>