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Date: Tue, 19 Mar 2024 12:44:09 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
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>
Cc: linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH][next] integrity: Avoid -Wflex-array-member-not-at-end
warnings
Hi all,
Friendly ping: who can take this, please? :)
Thanks!
--
Gustavo
On 3/4/24 11:52, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
> ready to enable it globally.
>
> There is currently an object (`hdr)` in `struct ima_max_digest_data`
> that contains a flexible structure (`struct ima_digest_data`):
>
> struct ima_max_digest_data {
> struct ima_digest_data hdr;
> u8 digest[HASH_MAX_DIGESTSIZE];
> } __packed;
>
> So, in order to avoid ending up with a flexible-array member in the
> middle of another struct, we use the `struct_group_tagged()` helper to
> separate the flexible array from the rest of the members in the flexible
> structure:
>
> struct ima_digest_data {
> struct_group_tagged(ima_digest_data_hdr, hdr,
>
> ... the rest of the members
>
> );
> u8 digest[];
> } __packed;
>
> With the change described above, we can now declare an object of the
> type of the tagged struct, without embedding the flexible array in the
> middle of another struct:
>
> struct ima_max_digest_data {
> struct ima_digest_data_hdr hdr;
> u8 digest[HASH_MAX_DIGESTSIZE];
> } __packed;
>
> We also use `container_of()` whenever we need to retrieve a pointer to
> the flexible structure.
>
> So, with these changes, fix the following warnings:
>
> security/integrity/evm/evm.h:45:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> security/integrity/evm/evm.h:45:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> security/integrity/evm/evm.h:45:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
> security/integrity/ima/ima_api.c | 6 ++++--
> security/integrity/ima/ima_appraise.c | 4 +++-
> security/integrity/ima/ima_init.c | 6 ++++--
> security/integrity/ima/ima_main.c | 6 ++++--
> security/integrity/ima/ima_template_lib.c | 10 ++++++----
> security/integrity/integrity.h | 4 +++-
> 6 files changed, 24 insertions(+), 12 deletions(-)
>
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index b37d043d5748..c7c8d1bffb17 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -247,6 +247,8 @@ int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
> struct inode *real_inode = d_real_inode(file_dentry(file));
> const char *filename = file->f_path.dentry->d_name.name;
> struct ima_max_digest_data hash;
> + struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
> + struct ima_digest_data, hdr);
> struct kstat stat;
> int result = 0;
> int length;
> @@ -286,9 +288,9 @@ int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
> result = -ENODATA;
> }
> } else if (buf) {
> - result = ima_calc_buffer_hash(buf, size, &hash.hdr);
> + result = ima_calc_buffer_hash(buf, size, hash_hdr);
> } else {
> - result = ima_calc_file_hash(file, &hash.hdr);
> + result = ima_calc_file_hash(file, hash_hdr);
> }
>
> if (result && result != -EBADF && result != -EINVAL)
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 3497741caea9..656c709b974f 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -378,7 +378,9 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
> }
>
> rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
> - iint->ima_hash->digest, &hash.hdr);
> + iint->ima_hash->digest,
> + container_of(&hash.hdr,
> + struct ima_digest_data, hdr));
> if (rc) {
> *cause = "sigv3-hashing-error";
> *status = INTEGRITY_FAIL;
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 393f5c7912d5..4e208239a40e 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -48,12 +48,14 @@ static int __init ima_add_boot_aggregate(void)
> struct ima_event_data event_data = { .iint = iint,
> .filename = boot_aggregate_name };
> struct ima_max_digest_data hash;
> + struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
> + struct ima_digest_data, hdr);
> int result = -ENOMEM;
> int violation = 0;
>
> memset(iint, 0, sizeof(*iint));
> memset(&hash, 0, sizeof(hash));
> - iint->ima_hash = &hash.hdr;
> + iint->ima_hash = hash_hdr;
> iint->ima_hash->algo = ima_hash_algo;
> iint->ima_hash->length = hash_digest_size[ima_hash_algo];
>
> @@ -70,7 +72,7 @@ static int __init ima_add_boot_aggregate(void)
> * is not found.
> */
> if (ima_tpm_chip) {
> - result = ima_calc_boot_aggregate(&hash.hdr);
> + result = ima_calc_boot_aggregate(hash_hdr);
> if (result < 0) {
> audit_cause = "hashing_error";
> goto err_out;
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index c84e8c55333d..0d3a7c864fd4 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -941,6 +941,8 @@ int process_buffer_measurement(struct mnt_idmap *idmap,
> .buf_len = size};
> struct ima_template_desc *template;
> struct ima_max_digest_data hash;
> + struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
> + struct ima_digest_data, hdr);
> char digest_hash[IMA_MAX_DIGEST_SIZE];
> int digest_hash_len = hash_digest_size[ima_hash_algo];
> int violation = 0;
> @@ -979,7 +981,7 @@ int process_buffer_measurement(struct mnt_idmap *idmap,
> if (!pcr)
> pcr = CONFIG_IMA_MEASURE_PCR_IDX;
>
> - iint.ima_hash = &hash.hdr;
> + iint.ima_hash = hash_hdr;
> iint.ima_hash->algo = ima_hash_algo;
> iint.ima_hash->length = hash_digest_size[ima_hash_algo];
>
> @@ -990,7 +992,7 @@ int process_buffer_measurement(struct mnt_idmap *idmap,
> }
>
> if (buf_hash) {
> - memcpy(digest_hash, hash.hdr.digest, digest_hash_len);
> + memcpy(digest_hash, hash_hdr->digest, digest_hash_len);
>
> ret = ima_calc_buffer_hash(digest_hash, digest_hash_len,
> iint.ima_hash);
> diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
> index 6cd0add524cd..74198d7619da 100644
> --- a/security/integrity/ima/ima_template_lib.c
> +++ b/security/integrity/ima/ima_template_lib.c
> @@ -339,6 +339,8 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
> struct ima_field_data *field_data)
> {
> struct ima_max_digest_data hash;
> + struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
> + struct ima_digest_data, hdr);
> u8 *cur_digest = NULL;
> u32 cur_digestsize = 0;
> struct inode *inode;
> @@ -358,7 +360,7 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
> if ((const char *)event_data->filename == boot_aggregate_name) {
> if (ima_tpm_chip) {
> hash.hdr.algo = HASH_ALGO_SHA1;
> - result = ima_calc_boot_aggregate(&hash.hdr);
> + result = ima_calc_boot_aggregate(hash_hdr);
>
> /* algo can change depending on available PCR banks */
> if (!result && hash.hdr.algo != HASH_ALGO_SHA1)
> @@ -368,7 +370,7 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
> memset(&hash, 0, sizeof(hash));
> }
>
> - cur_digest = hash.hdr.digest;
> + cur_digest = hash_hdr->digest;
> cur_digestsize = hash_digest_size[HASH_ALGO_SHA1];
> goto out;
> }
> @@ -379,14 +381,14 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
> inode = file_inode(event_data->file);
> hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
> ima_hash_algo : HASH_ALGO_SHA1;
> - result = ima_calc_file_hash(event_data->file, &hash.hdr);
> + result = ima_calc_file_hash(event_data->file, hash_hdr);
> if (result) {
> integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
> event_data->filename, "collect_data",
> "failed", result, 0);
> return result;
> }
> - cur_digest = hash.hdr.digest;
> + cur_digest = hash_hdr->digest;
> cur_digestsize = hash.hdr.length;
> out:
> return ima_eventdigest_init_common(cur_digest, cur_digestsize,
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 50d6f798e613..fc1952da02ea 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -44,6 +44,7 @@ struct evm_xattr {
> #define IMA_MAX_DIGEST_SIZE HASH_MAX_DIGESTSIZE
>
> struct ima_digest_data {
> + struct_group_tagged(ima_digest_data_hdr, hdr,
> u8 algo;
> u8 length;
> union {
> @@ -57,6 +58,7 @@ struct ima_digest_data {
> } ng;
> u8 data[2];
> } xattr;
> + );
> u8 digest[];
> } __packed;
>
> @@ -65,7 +67,7 @@ struct ima_digest_data {
> * with the maximum hash size, define ima_max_digest_data struct.
> */
> struct ima_max_digest_data {
> - struct ima_digest_data hdr;
> + struct ima_digest_data_hdr hdr;
> u8 digest[HASH_MAX_DIGESTSIZE];
> } __packed;
>
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