[PATCH v2] ima_fs: Avoid creating measurement lists for unsupported hash algos

From: Dmitry Safonov <redacted>

ima_init_crypto() skips initializing ima_algo_array[i] if the alogorithm
from ima_tpm_chip->allocated_banks[i].crypto_id is not supported.
It seems avoid adding the unsupported algorithm to ima_algo_array will
break all the logic that relies on indexing by NR_BANKS(ima_tpm_chip).

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

quoted

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

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x107ce18
flags: 0x8000000000002000(reserved|zone=2)
raw: 8000000000002000 ffffea0041f38608 ffffea0041f38608 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

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

quoted

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:

quoted

tpm tpm0: TPM with unsupported bank algorithm 0x0027

Grepping HASH_ALGO__LAST in security/integrity/ima/ shows that is
the check other logic relies on, so add files under TPM_ALG_<ID>
and print 0 as their hash_digest_size.

This is how it looks on the test machine I have:

quoted

# 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

Fixes: 9fa8e7625008 ("ima: add crypto agility support for template-hash algorithm")
Signed-off-by: Dmitry Safonov <redacted>
Cc: Enrico Bravi <redacted>
Cc: Silvia Sisinni <redacted>
Cc: Roberto Sassu <roberto.sassu@huawei.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
---
Changes in v2:
- Instead of skipping unknown algorithms, add files under their TPM_ALG_ID (Roberto Sassu)
- Fix spelling (Roberto Sassu)
- Copy @stable on the fix
- Link to v1: https://lore.kernel.org/r/20260127-ima-oob-v1-1-2d42f3418e57@arista.com
---
 security/integrity/ima/ima_fs.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 012a58959ff0..3b442e3f84d0 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c

@@ -160,7 +160,10 @@ int ima_measurements_show(struct seq_file *m, void *v)
 	ima_putc(m, &pcr, sizeof(e->pcr));
 
 	/* 2nd: template digest */
-	ima_putc(m, e->digests[algo_idx].digest, hash_digest_size[algo]);
+	if (algo == HASH_ALGO__LAST)
+		ima_putc(m, "0", 1);
+	else
+		ima_putc(m, e->digests[algo_idx].digest, hash_digest_size[algo]);
 
 	/* 3rd: template name size */
 	namelen = !ima_canonical_fmt ? strlen(template_name) :

@@ -252,7 +255,10 @@ static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 	seq_printf(m, "%2d ", e->pcr);
 
 	/* 2nd: template hash */
-	ima_print_digest(m, e->digests[algo_idx].digest, hash_digest_size[algo]);
+	if (algo == HASH_ALGO__LAST)
+		ima_putc(m, "0", 1);
+	else
+		ima_print_digest(m, e->digests[algo_idx].digest, hash_digest_size[algo]);

 
 	/* 3th:  template name */
 	seq_printf(m, " %s", template_name);

@@ -404,16 +410,24 @@ static int __init create_securityfs_measurement_lists(void)
 		char file_name[NAME_MAX + 1];
 		struct dentry *dentry;
 
-		sprintf(file_name, "ascii_runtime_measurements_%s",
-			hash_algo_name[algo]);
+		if (algo == HASH_ALGO__LAST)
+			sprintf(file_name, "ascii_runtime_measurements_TPM_ALG_%x",
+				ima_tpm_chip->allocated_banks[i].alg_id);
+		else
+			sprintf(file_name, "ascii_runtime_measurements_%s",
+				hash_algo_name[algo]);
 		dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
 						ima_dir, (void *)(uintptr_t)i,
 						&ima_ascii_measurements_ops);
 		if (IS_ERR(dentry))
 			return PTR_ERR(dentry);
 
-		sprintf(file_name, "binary_runtime_measurements_%s",
-			hash_algo_name[algo]);
+		if (algo == HASH_ALGO__LAST)
+			sprintf(file_name, "binary_runtime_measurements_TPM_ALG_%x",
+				ima_tpm_chip->allocated_banks[i].alg_id);
+		else
+			sprintf(file_name, "binary_runtime_measurements_%s",
+				hash_algo_name[algo]);
 		dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
 						ima_dir, (void *)(uintptr_t)i,
 						&ima_measurements_ops);

---
base-commit: 63804fed149a6750ffd28610c5c1c98cce6bd377
change-id: 20260127-ima-oob-9fa83a634d7b

Best regards,