| Message ID | Zg7AoOh7CL5ZD/fe@neat (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v5,next] integrity: Avoid -Wflex-array-member-not-at-end warnings | expand |
Hi Gustavo, On Thu, 2024-04-04 at 09:00 -0600, 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 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@kernel.org> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Thanks, Gustavo. I already applied and tested v4, but was trying to actually see the errors with before pushing it out. Mimi
On Thu, 2024-04-04 at 12:49 -0400, Mimi Zohar wrote: > Hi Gustavo, > > On Thu, 2024-04-04 at 09:00 -0600, 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 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@kernel.org> > > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> > > Thanks, Gustavo. I already applied and tested v4, but was trying to actually > see the errors with before pushing it out. With GCC-14, I'm seeing the "warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]" messages. As expected, with the patch no warnings. "checkpatch.pl --strict" complains "CHECK: Alignment should match open parenthesis". I'll queue the patch, but how about teaching checkpatch.pl to ignore __struct_group()? thanks, Mimi
> "checkpatch.pl --strict" complains "CHECK: Alignment should match open > parenthesis". I'll queue the patch, but how about teaching checkpatch.pl to > ignore __struct_group()? I think this would do it: diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 9c4c4a61bc83..e229b97f17f6 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -3958,7 +3958,7 @@ sub process { my $rest = $2; my $pos = pos_last_openparen($rest); - if ($pos >= 0) { + if ($pos >= 0 && $rest !~ /(__)?struct_group(_(tagged|attr))?(\()/) { $line =~ /^(\+| )([ \t]*)/; my $newindent = $2; I'll send a proper patch. Thanks for the suggestion, Mimi. -- Gustavo
On Thu, 2024-04-04 at 18:56 -0600, Gustavo A. R. Silva wrote: > > "checkpatch.pl --strict" complains "CHECK: Alignment should match open > > parenthesis". I'll queue the patch, but how about teaching checkpatch.pl to > > ignore __struct_group()? > > I think this would do it: > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > index 9c4c4a61bc83..e229b97f17f6 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -3958,7 +3958,7 @@ sub process { > my $rest = $2; > > my $pos = pos_last_openparen($rest); > - if ($pos >= 0) { > + if ($pos >= 0 && $rest !~ > /(__)?struct_group(_(tagged|attr))?(\()/) { > $line =~ /^(\+| )([ \t]*)/; > my $newindent = $2; > > I'll send a proper patch. Thanks for the suggestion, Mimi. Thanks, it works. Mimi
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 1856981e33df..3d286de231e1 100644 --- a/security/integrity/ima/ima_api.c +++ b/security/integrity/ima/ima_api.c @@ -246,6 +246,8 @@ int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file, struct inode *inode = file_inode(file); struct inode *real_inode = d_real_inode(file_dentry(file)); struct ima_max_digest_data hash; + struct ima_digest_data *hash_hdr = container_of(&hash.hdr, + struct ima_digest_data, hdr); struct name_snapshot filename; struct kstat stat; int result = 0; @@ -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 4b4348d681a6..fff155f230a5 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -948,6 +948,8 @@ 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; @@ -986,7 +988,7 @@ 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]; @@ -997,7 +999,7 @@ 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 3b2cb8f1002e..4183956c53af 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;
-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@kernel.org> --- Changes in v5: - Rebase patch. Changes in v4: - Update changelog text. (Mimi Zohar) - Include changes for `struct evm_xattr`. - Add a couple of code comments. - Link: https://lore.kernel.org/linux-hardening/ZgsAFhl90kecIR00@neat/ 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(-)