From: GUO Zihua <guozihua@huawei.com>
To: <linux-integrity@vger.kernel.org>
Cc: <zohar@linux.ibm.com>, <dmitry.kasatkin@gmail.com>,
<gustavoars@kernel.org>, <linux-hardening@vger.kernel.org>
Subject: [PATCH v2] evm: Refector struct evm_xattr
Date: Wed, 18 May 2022 14:32:32 +0800 [thread overview]
Message-ID: <20220518063232.239089-1-guozihua@huawei.com> (raw)
struct evm_xattr is only used for EVM_XATTR_HMAC type evm digest and
glues together one flexible array and one fixed length array. The
original intention might be shortening the code as the "data" field
would always be a SHA1 digest.
This implementation is not complying with GCC's specification about
flexible array which requires that flexible should be the last member of
a structure and structure of flexible array should not be a sub
structure.
Fix it by:
1. Remove struct evm_xattr and use struct evm_ima_xattr_data directly.
2. Get array size with struct_size instead of sizeof as suggested by
Linus.
Reference: https://lore.kernel.org/all/CAHk-=wiGWjxs7EVUpccZEi6esvjpHJdgHQ=vtUeJ5crL62hx9A@mail.gmail.com/
Fixes: 6be5cc5246f80 ("evm: add support for different security.evm data types")
Signed-off-by: GUO Zihua <guozihua@huawei.com>
---
v2:
Change the patch subject to PATCH instead of PATCH -next. Update
commit message based on feedback from Gustavo on another patch.
---
security/integrity/evm/evm_main.c | 14 ++++++++------
security/integrity/integrity.h | 6 ------
2 files changed, 8 insertions(+), 12 deletions(-)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 7d87772f0ce6..f2c4501a287a 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -211,7 +211,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
/* check value type */
switch (xattr_data->type) {
case EVM_XATTR_HMAC:
- if (xattr_len != sizeof(struct evm_xattr)) {
+ if (xattr_len != struct_size(*xattr_data, data,
+ SHA1_DIGEST_SIZE)) {
evm_status = INTEGRITY_FAIL;
goto out;
}
@@ -842,24 +843,25 @@ int evm_inode_init_security(struct inode *inode,
const struct xattr *lsm_xattr,
struct xattr *evm_xattr)
{
- struct evm_xattr *xattr_data;
+ struct evm_ima_xattr_data *xattr_data;
int rc;
if (!(evm_initialized & EVM_INIT_HMAC) ||
!evm_protected_xattr(lsm_xattr->name))
return 0;
- xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
+ xattr_data = kzalloc(struct_size(*xattr_data, data,
+ SHA1_DIGEST_SIZE), GFP_NOFS);
if (!xattr_data)
return -ENOMEM;
- xattr_data->data.type = EVM_XATTR_HMAC;
- rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
+ xattr_data->type = EVM_XATTR_HMAC;
+ rc = evm_init_hmac(inode, lsm_xattr, xattr_data->data);
if (rc < 0)
goto out;
evm_xattr->value = xattr_data;
- evm_xattr->value_len = sizeof(*xattr_data);
+ evm_xattr->value_len = struct_size(*xattr_data, data, SHA1_DIGEST_SIZE);
evm_xattr->name = XATTR_EVM_SUFFIX;
return 0;
out:
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 3510e413ea17..91b16d620dd9 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -86,12 +86,6 @@ struct evm_ima_xattr_data {
u8 data[];
} __packed;
-/* Only used in the EVM HMAC code. */
-struct evm_xattr {
- struct evm_ima_xattr_data data;
- u8 digest[SHA1_DIGEST_SIZE];
-} __packed;
-
#define IMA_MAX_DIGEST_SIZE 64
struct ima_digest_data {
--
2.36.0
reply other threads:[~2022-05-18 6:34 UTC|newest]
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