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Subject[PATCH v5 04/12] ima: Move ima_reset_appraise_flags() call to post hooks
Date
ima_inode_setxattr() and ima_inode_removexattr() hooks are called before an
operation is performed. Thus, ima_reset_appraise_flags() should not be
called there, as flags might be unnecessarily reset if the operation is
denied.

This patch introduces the post hooks ima_inode_post_setxattr() and
ima_inode_post_removexattr(), and adds the call to
ima_reset_appraise_flags() in the new functions.

Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
fs/xattr.c | 2 ++
include/linux/ima.h | 18 ++++++++++++++++++
security/integrity/ima/ima_appraise.c | 25 ++++++++++++++++++++++---
security/security.c | 1 +
4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/fs/xattr.c b/fs/xattr.c
index b3444e06cded..81847f132d26 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -16,6 +16,7 @@
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/evm.h>
+#include <linux/ima.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/fsnotify.h>
@@ -502,6 +503,7 @@ __vfs_removexattr_locked(struct user_namespace *mnt_userns,

if (!error) {
fsnotify_xattr(dentry);
+ ima_inode_post_removexattr(dentry, name);
evm_inode_post_removexattr(dentry, name);
}

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 61d5723ec303..5e059da43857 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -171,7 +171,13 @@ extern void ima_inode_post_setattr(struct user_namespace *mnt_userns,
struct dentry *dentry);
extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len);
+extern void ima_inode_post_setxattr(struct dentry *dentry,
+ const char *xattr_name,
+ const void *xattr_value,
+ size_t xattr_value_len);
extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
+extern void ima_inode_post_removexattr(struct dentry *dentry,
+ const char *xattr_name);
#else
static inline bool is_ima_appraise_enabled(void)
{
@@ -192,11 +198,23 @@ static inline int ima_inode_setxattr(struct dentry *dentry,
return 0;
}

+static inline void ima_inode_post_setxattr(struct dentry *dentry,
+ const char *xattr_name,
+ const void *xattr_value,
+ size_t xattr_value_len)
+{
+}
+
static inline int ima_inode_removexattr(struct dentry *dentry,
const char *xattr_name)
{
return 0;
}
+
+static inline void ima_inode_post_removexattr(struct dentry *dentry,
+ const char *xattr_name)
+{
+}
#endif /* CONFIG_IMA_APPRAISE */

#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 565e33ff19d0..1f029e4c8d7f 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
if (result == 1) {
if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
return -EINVAL;
- ima_reset_appraise_flags(d_backing_inode(dentry),
- xvalue->type == EVM_IMA_XATTR_DIGSIG);
result = 0;
}
return result;
}

+void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
+ const void *xattr_value, size_t xattr_value_len)
+{
+ const struct evm_ima_xattr_data *xvalue = xattr_value;
+ int result;
+
+ result = ima_protect_xattr(dentry, xattr_name, xattr_value,
+ xattr_value_len);
+ if (result == 1)
+ ima_reset_appraise_flags(d_backing_inode(dentry),
+ xvalue->type == EVM_IMA_XATTR_DIGSIG);
+}
+
int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
{
int result;

result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
if (result == 1) {
- ima_reset_appraise_flags(d_backing_inode(dentry), 0);
result = 0;
}
return result;
}
+
+void ima_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+ int result;
+
+ result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
+ if (result == 1)
+ ima_reset_appraise_flags(d_backing_inode(dentry), 0);
+}
diff --git a/security/security.c b/security/security.c
index 5ac96b16f8fa..efb1f874dc41 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1319,6 +1319,7 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name,
if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
return;
call_void_hook(inode_post_setxattr, dentry, name, value, size, flags);
+ ima_inode_post_setxattr(dentry, name, value, size);
evm_inode_post_setxattr(dentry, name, value, size);
}

--
2.26.2
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