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Message-Id: <20260127-ima-oob-v3-1-1dd09f4c2a6a@arista.com>
Date: Tue, 27 Jan 2026 14:21:13 +0000
From: Dmitry Safonov via B4 Relay <devnull+dima.arista.com@...nel.org>
To: Mimi Zohar <zohar@...ux.ibm.com>,
Roberto Sassu <roberto.sassu@...wei.com>,
Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
Eric Snowberg <eric.snowberg@...cle.com>, Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
Silvia Sisinni <silvia.sisinni@...ito.it>,
Enrico Bravi <enrico.bravi@...ito.it>
Cc: linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Dmitry Safonov <0x7f454c46@...il.com>, Dmitry Safonov <dima@...sta.com>
Subject: [PATCH v3] ima_fs: Avoid creating measurement lists for
unsupported hash algos
From: Dmitry Safonov <dima@...sta.com>
ima_init_crypto() skips initializing ima_algo_array[i] if the algorithm
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:
> ==================================================================
> 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
> >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
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:
> # 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 <dima@...sta.com>
Cc: Enrico Bravi <enrico.bravi@...ito.it>
Cc: Silvia Sisinni <silvia.sisinni@...ito.it>
Cc: Roberto Sassu <roberto.sassu@...wei.com>
Cc: Mimi Zohar <zohar@...ux.ibm.com>
---
Changes in v3:
- Now fix the spelling *for real* (sorry, messed it up in v2)
- Link to v2: https://lore.kernel.org/r/20260127-ima-oob-v2-1-f38a18c850cf@arista.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,
--
Dmitry Safonov <dima@...sta.com>
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