[PATCH v4][next] integrity: Avoid -Wflex-array-member-not-at-end warnings

From: Gustavo A. R. Silva
Date: Mon Apr 01 2024 - 14:42:40 EST

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-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 a struct, we use the `__struct_group()` helper to separate
the flexible array from the rest of the members in the flexible
structure:

struct ima_digest_data {
__struct_group(ima_digest_data_hdr, hdr, __packed,

... the rest of the members

);
u8 digest[];
} __packed;

And similarly for `struct evm_ima_xattr_data`.

With the change described above, we can now declare an object of the
type of the tagged `struct ima_digest_data_hdr`, 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;

And similarly for `struct evm_digest` and `struct evm_xattr`.

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:64:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/evm/../integrity.h:40:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/evm/../integrity.h:68:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/ima/../integrity.h:40:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/ima/../integrity.h:68:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/integrity.h:40:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/integrity.h:68:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/platform_certs/../integrity.h:40:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
security/integrity/platform_certs/../integrity.h:68:32: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Link: https://github.com/KSPP/linux/issues/202
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
Changes in v4:
- Update changelog text. (Mimi Zohar)
- Include changes for `struct evm_ima_xattr_data` and `struct evm_xattr`.
- Add a couple of code comments.

Changes in v3:
- struct ima_digest_data is a packed structure. So, to keep things
consistent, use the attribute __packed on the tagged struct
ima_digest_data_hdr. For this, we use __struct_group() instead of
struct_group_tagged(). Update the changelog text, accordingly.
- Link: https://lore.kernel.org/linux-hardening/ZfuzWku+ip4fsZrb@neat/

Changes in v2:
- Include changes for `struct evm_digest` (Mimi Zohar)
- Link: https://lore.kernel.org/linux-hardening/ZfuvoIj+AJHjCdTs@neat/

v1:
- Link: https://lore.kernel.org/linux-hardening/ZeYKWrXvACBBrAP8@neat/

security/integrity/evm/evm.h | 2 +-
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 | 12 +++++++++---
7 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index eb1a2c343bd7..72e3341ae6f7 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -61,7 +61,7 @@ extern int evm_hmac_attrs;
extern struct list_head evm_config_xattrnames;

struct evm_digest {
- struct ima_digest_data hdr;
+ struct ima_digest_data_hdr hdr;
char digest[IMA_MAX_DIGEST_SIZE];
} __packed;

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..660f76cb69d3 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -31,19 +31,24 @@ enum evm_ima_xattr_type {
};

struct evm_ima_xattr_data {
- u8 type;
+ /* New members must be added within the __struct_group() macro below. */
+ __struct_group(evm_ima_xattr_data_hdr, hdr, __packed,
+ u8 type;
+ );
u8 data[];
} __packed;

/* Only used in the EVM HMAC code. */
struct evm_xattr {
- struct evm_ima_xattr_data data;
+ struct evm_ima_xattr_data_hdr data;
u8 digest[SHA1_DIGEST_SIZE];
} __packed;

#define IMA_MAX_DIGEST_SIZE HASH_MAX_DIGESTSIZE

struct ima_digest_data {
+ /* New members must be added within the __struct_group() macro below. */
+ __struct_group(ima_digest_data_hdr, hdr, __packed,
u8 algo;
u8 length;
union {
@@ -57,6 +62,7 @@ struct ima_digest_data {
} ng;
u8 data[2];
} xattr;
+ );
u8 digest[];
} __packed;

@@ -65,7 +71,7 @@ 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;

--
2.34.1

Next message: Dmitry Baryshkov: "Re: [PATCH v2 0/7] arm64: dts: qcom: fix description of the Type-C signals"
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