[PATCH v6 07/11] evm: Pass user namespace to set/remove xattr hooks

Roberto Sassu
2021-05-05T11:34:02Z

In preparation for 'evm: Allow setxattr() and setattr() for unmodified
metadata', this patch passes mnt_userns to the inode set/remove xattr hooks
so that the GID of the inode on an idmapped mount is correctly determined
by posix_acl_update_mode().

Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
---
include/linux/evm.h | 12 ++++++++----
security/integrity/evm/evm_main.c | 17 +++++++++++------
security/security.c | 4 ++--
3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/include/linux/evm.h b/include/linux/evm.h
index e5b7bcb152b9..8cad46bcec9d 100644
--- a/include/linux/evm.h
+++ b/include/linux/evm.h
@@ -23,13 +23,15 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
struct integrity_iint_cache *iint);
extern int evm_inode_setattr(struct dentry *dentry, struct iattr *attr);
extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid);
-extern int evm_inode_setxattr(struct dentry *dentry, const char *name,
+extern int evm_inode_setxattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, const char *name,
const void *value, size_t size);
extern void evm_inode_post_setxattr(struct dentry *dentry,
const char *xattr_name,
const void *xattr_value,
size_t xattr_value_len);
-extern int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name);
+extern int evm_inode_removexattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, const char *xattr_name);
extern void evm_inode_post_removexattr(struct dentry *dentry,
const char *xattr_name);
extern int evm_inode_init_security(struct inode *inode,
@@ -72,7 +74,8 @@ static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
return;
}

-static inline int evm_inode_setxattr(struct dentry *dentry, const char *name,
+static inline int evm_inode_setxattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, const char *name,
const void *value, size_t size)
{
return 0;
@@ -86,7 +89,8 @@ static inline void evm_inode_post_setxattr(struct dentry *dentry,
return;
}

-static inline int evm_inode_removexattr(struct dentry *dentry,
+static inline int evm_inode_removexattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry,
const char *xattr_name)
{
return 0;
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 9faebff029e6..3745c08c09e6 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -342,7 +342,8 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
* For posix xattr acls only, permit security.evm, even if it currently
* doesn't exist, to be updated unless the EVM signature is immutable.
*/
-static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
+static int evm_protect_xattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
enum integrity_status evm_status;
@@ -405,6 +406,7 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,

/**
* evm_inode_setxattr - protect the EVM extended attribute
+ * @mnt_userns: user namespace of the idmapped mount
* @dentry: pointer to the affected dentry
* @xattr_name: pointer to the affected extended attribute name
* @xattr_value: pointer to the new extended attribute value
@@ -416,8 +418,9 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
* userspace from writing HMAC value. Writing 'security.evm' requires
* requires CAP_SYS_ADMIN privileges.
*/
-int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
- const void *xattr_value, size_t xattr_value_len)
+int evm_inode_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+ const char *xattr_name, const void *xattr_value,
+ size_t xattr_value_len)
{
const struct evm_ima_xattr_data *xattr_data = xattr_value;

@@ -434,19 +437,21 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
return -EPERM;
}
- return evm_protect_xattr(dentry, xattr_name, xattr_value,
+ return evm_protect_xattr(mnt_userns, dentry, xattr_name, xattr_value,
xattr_value_len);
}

/**
* evm_inode_removexattr - protect the EVM extended attribute
+ * @mnt_userns: user namespace of the idmapped mount
* @dentry: pointer to the affected dentry
* @xattr_name: pointer to the affected extended attribute name
*
* Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
* the current value is valid.
*/
-int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
+int evm_inode_removexattr(struct user_namespace *mnt_userns,
+ struct dentry *dentry, const char *xattr_name)
{
/* Policy permits modification of the protected xattrs even though
* there's no HMAC key loaded
@@ -454,7 +459,7 @@ int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
return 0;

- return evm_protect_xattr(dentry, xattr_name, NULL, 0);
+ return evm_protect_xattr(mnt_userns, dentry, xattr_name, NULL, 0);
}

static void evm_reset_status(struct inode *inode)
diff --git a/security/security.c b/security/security.c
index b38155b2de83..e9f8010a2341 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1354,7 +1354,7 @@ int security_inode_setxattr(struct user_namespace *mnt_userns,
ret = ima_inode_setxattr(dentry, name, value, size);
if (ret)
return ret;
- return evm_inode_setxattr(dentry, name, value, size);
+ return evm_inode_setxattr(mnt_userns, dentry, name, value, size);
}

void security_inode_post_setxattr(struct dentry *dentry, const char *name,
@@ -1399,7 +1399,7 @@ int security_inode_removexattr(struct user_namespace *mnt_userns,
ret = ima_inode_removexattr(dentry, name);
if (ret)
return ret;
- return evm_inode_removexattr(dentry, name);
+ return evm_inode_removexattr(mnt_userns, dentry, name);
}

int security_inode_need_killpriv(struct dentry *dentry)
--
2.25.1