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ima_fs: Correctly create securityfs files for unsupported hash algos

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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>
This commit is contained in:
Dmitry Safonov
2026-03-10 17:40:39 +00:00
committed by Mimi Zohar
parent 870819434c
commit d7bd8cf0b3
1 changed files with 12 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
security/integrity/ima/ima_fs.c
View File

@@ -398,16 +398,24 @@ 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);