On 3/3/2023 10:26 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> As for IMA, remove hardcoded EVM function calls from the LSM infrastructure
> and the VFS. Make EVM functions as static (except for
> evm_inode_init_security(), which is exported), and register them as hook
> implementations in init_evm_lsm(), called from integrity_lsm_init().
>
> Finally, switch to the LSM reservation mechanism for the EVM xattr, by
> setting the lbs_xattr field of the lsm_blob_sizes structure, and
> consequently decrement the number of xattrs to allocate in
> security_inode_init_security().
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
> fs/attr.c | 2 -
> fs/posix_acl.c | 3 -
> fs/xattr.c | 2 -
> include/linux/evm.h | 116 ------------------------------
> security/integrity/evm/evm_main.c | 106 ++++++++++++++++++++++-----
> security/integrity/iint.c | 7 ++
> security/integrity/integrity.h | 9 +++
> security/security.c | 41 +++--------
> 8 files changed, 115 insertions(+), 171 deletions(-)
>
> diff --git a/fs/attr.c b/fs/attr.c
> index 406d782dfab..1b911a627fe 100644
> --- a/fs/attr.c
> +++ b/fs/attr.c
> @@ -16,7 +16,6 @@
> #include <linux/fcntl.h>
> #include <linux/filelock.h>
> #include <linux/security.h>
> -#include <linux/evm.h>
>
> #include "internal.h"
>
> @@ -485,7 +484,6 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
> if (!error) {
> fsnotify_change(dentry, ia_valid);
> security_inode_post_setattr(idmap, dentry, ia_valid);
> - evm_inode_post_setattr(idmap, dentry, ia_valid);
> }
>
> return error;
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 5b8c92fce0c..608cb0a9f84 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -26,7 +26,6 @@
> #include <linux/mnt_idmapping.h>
> #include <linux/iversion.h>
> #include <linux/security.h>
> -#include <linux/evm.h>
> #include <linux/fsnotify.h>
> #include <linux/filelock.h>
>
> @@ -1103,7 +1102,6 @@ int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> if (!error) {
> fsnotify_xattr(dentry);
> security_inode_post_set_acl(dentry, acl_name, kacl);
> - evm_inode_post_set_acl(dentry, acl_name, kacl);
> }
>
> out_inode_unlock:
> @@ -1214,7 +1212,6 @@ int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> if (!error) {
> fsnotify_xattr(dentry);
> security_inode_post_remove_acl(idmap, dentry, acl_name);
> - evm_inode_post_remove_acl(idmap, dentry, acl_name);
> }
>
> out_inode_unlock:
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 10c959d9fc6..7708ffdacca 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -16,7 +16,6 @@
> #include <linux/mount.h>
> #include <linux/namei.h>
> #include <linux/security.h>
> -#include <linux/evm.h>
> #include <linux/syscalls.h>
> #include <linux/export.h>
> #include <linux/fsnotify.h>
> @@ -535,7 +534,6 @@ __vfs_removexattr_locked(struct mnt_idmap *idmap,
> if (!error) {
> fsnotify_xattr(dentry);
> security_inode_post_removexattr(dentry, name);
> - evm_inode_post_removexattr(dentry, name);
> }
>
> out:
> diff --git a/include/linux/evm.h b/include/linux/evm.h
> index 8c043273552..61794299f09 100644
> --- a/include/linux/evm.h
> +++ b/include/linux/evm.h
> @@ -21,46 +21,6 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
> void *xattr_value,
> size_t xattr_value_len,
> struct integrity_iint_cache *iint);
> -extern int evm_inode_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, struct iattr *attr);
> -extern void evm_inode_post_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, int ia_valid);
> -extern int evm_inode_setxattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *name,
> - const void *value, size_t size, int flags);
> -extern void evm_inode_post_setxattr(struct dentry *dentry,
> - const char *xattr_name,
> - const void *xattr_value,
> - size_t xattr_value_len,
> - int flags);
> -extern int evm_inode_removexattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *xattr_name);
> -extern void evm_inode_post_removexattr(struct dentry *dentry,
> - const char *xattr_name);
> -static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - evm_inode_post_removexattr(dentry, acl_name);
> -}
> -extern int evm_inode_set_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *acl_name,
> - struct posix_acl *kacl);
> -static inline int evm_inode_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
> -}
> -static inline void evm_inode_post_set_acl(struct dentry *dentry,
> - const char *acl_name,
> - struct posix_acl *kacl)
> -{
> - return evm_inode_post_setxattr(dentry, acl_name, NULL, 0, 0);
> -}
> -extern int evm_inode_init_security(struct inode *inode, struct inode *dir,
> - const struct qstr *qstr,
> - struct xattr *xattrs);
> extern bool evm_revalidate_status(const char *xattr_name);
> extern int evm_protected_xattr_if_enabled(const char *req_xattr_name);
> extern int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
> @@ -92,82 +52,6 @@ static inline enum integrity_status evm_verifyxattr(struct dentry *dentry,
> }
> #endif
>
> -static inline int evm_inode_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, struct iattr *attr)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, int ia_valid)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_setxattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *name,
> - const void *value, size_t size, int flags)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_setxattr(struct dentry *dentry,
> - const char *xattr_name,
> - const void *xattr_value,
> - size_t xattr_value_len,
> - int flags)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_removexattr(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *xattr_name)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_removexattr(struct dentry *dentry,
> - const char *xattr_name)
> -{
> - return;
> -}
> -
> -static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_set_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *acl_name,
> - struct posix_acl *kacl)
> -{
> - return 0;
> -}
> -
> -static inline int evm_inode_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_set_acl(struct dentry *dentry,
> - const char *acl_name,
> - struct posix_acl *kacl)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_init_security(struct inode *inode, struct inode *dir,
> - const struct qstr *qstr,
> - struct xattr *xattrs)
> -{
> - return 0;
> -}
> -
> static inline bool evm_revalidate_status(const char *xattr_name)
> {
> return false;
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index 8b5c472f78b..c45bc97277c 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -19,6 +19,7 @@
> #include <linux/xattr.h>
> #include <linux/integrity.h>
> #include <linux/evm.h>
> +#include <linux/lsm_hooks.h>
> #include <linux/magic.h>
> #include <linux/posix_acl_xattr.h>
>
> @@ -566,9 +567,9 @@ static int evm_protect_xattr(struct mnt_idmap *idmap,
> * userspace from writing HMAC value. Writing 'security.evm' requires
> * requires CAP_SYS_ADMIN privileges.
> */
> -int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> - const char *xattr_name, const void *xattr_value,
> - size_t xattr_value_len, int flags)
> +static int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *xattr_name, const void *xattr_value,
> + size_t xattr_value_len, int flags)
> {
> const struct evm_ima_xattr_data *xattr_data = xattr_value;
>
> @@ -598,8 +599,8 @@ int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
> * the current value is valid.
> */
> -int evm_inode_removexattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *xattr_name)
> +static int evm_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *xattr_name)
> {
> /* Policy permits modification of the protected xattrs even though
> * there's no HMAC key loaded
> @@ -649,9 +650,11 @@ static inline int evm_inode_set_acl_change(struct mnt_idmap *idmap,
> * Prevent modifying posix acls causing the EVM HMAC to be re-calculated
> * and 'security.evm' xattr updated, unless the existing 'security.evm' is
> * valid.
> + *
> + * Return: zero on success, -EPERM on failure.
> */
> -int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> - const char *acl_name, struct posix_acl *kacl)
> +static int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *acl_name, struct posix_acl *kacl)
> {
> enum integrity_status evm_status;
>
> @@ -690,6 +693,24 @@ int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> return -EPERM;
> }
>
> +/**
> + * evm_inode_remove_acl - Protect the EVM extended attribute from posix acls
> + * @idmap: idmap of the mount
> + * @dentry: pointer to the affected dentry
> + * @acl_name: name of the posix acl
> + *
> + * Prevent removing posix acls causing the EVM HMAC to be re-calculated
> + * and 'security.evm' xattr updated, unless the existing 'security.evm' is
> + * valid.
> + *
> + * Return: zero on success, -EPERM on failure.
> + */
> +static int evm_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *acl_name)
> +{
> + return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
> +}
> +
> static void evm_reset_status(struct inode *inode)
> {
> struct integrity_iint_cache *iint;
> @@ -738,9 +759,11 @@ bool evm_revalidate_status(const char *xattr_name)
> * __vfs_setxattr_noperm(). The caller of which has taken the inode's
> * i_mutex lock.
> */
> -void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> - const void *xattr_value, size_t xattr_value_len,
> - int flags)
> +static void evm_inode_post_setxattr(struct dentry *dentry,
> + const char *xattr_name,
> + const void *xattr_value,
> + size_t xattr_value_len,
> + int flags)
> {
> if (!evm_revalidate_status(xattr_name))
> return;
> @@ -756,6 +779,21 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
> }
>
> +/**
> + * evm_inode_post_set_acl - Update the EVM extended attribute from posix acls
> + * @dentry: pointer to the affected dentry
> + * @acl_name: name of the posix acl
> + * @kacl: pointer to the posix acls
> + *
> + * Update the 'security.evm' xattr with the EVM HMAC re-calculated after setting
> + * posix acls.
> + */
> +static void evm_inode_post_set_acl(struct dentry *dentry, const char *acl_name,
> + struct posix_acl *kacl)
> +{
> + return evm_inode_post_setxattr(dentry, acl_name, NULL, 0, 0);
> +}
> +
> /**
> * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
> * @dentry: pointer to the affected dentry
> @@ -766,7 +804,8 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> * No need to take the i_mutex lock here, as this function is called from
> * vfs_removexattr() which takes the i_mutex.
> */
> -void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
> +static void evm_inode_post_removexattr(struct dentry *dentry,
> + const char *xattr_name)
> {
> if (!evm_revalidate_status(xattr_name))
> return;
> @@ -782,6 +821,22 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
> evm_update_evmxattr(dentry, xattr_name, NULL, 0);
> }
>
> +/**
> + * evm_inode_post_remove_acl - Update the EVM extended attribute from posix acls
> + * @idmap: idmap of the mount
> + * @dentry: pointer to the affected dentry
> + * @acl_name: name of the posix acl
> + *
> + * Update the 'security.evm' xattr with the EVM HMAC re-calculated after
> + * removing posix acls.
> + */
> +static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
> + struct dentry *dentry,
> + const char *acl_name)
> +{
> + evm_inode_post_removexattr(dentry, acl_name);
> +}
> +
> static int evm_attr_change(struct mnt_idmap *idmap,
> struct dentry *dentry, struct iattr *attr)
> {
> @@ -805,8 +860,8 @@ static int evm_attr_change(struct mnt_idmap *idmap,
> * Permit update of file attributes when files have a valid EVM signature,
> * except in the case of them having an immutable portable signature.
> */
> -int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> - struct iattr *attr)
> +static int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> + struct iattr *attr)
> {
> unsigned int ia_valid = attr->ia_valid;
> enum integrity_status evm_status;
> @@ -853,8 +908,8 @@ int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> * This function is called from notify_change(), which expects the caller
> * to lock the inode's i_mutex.
> */
> -void evm_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> - int ia_valid)
> +static void evm_inode_post_setattr(struct mnt_idmap *idmap,
> + struct dentry *dentry, int ia_valid)
> {
> if (!evm_revalidate_status(NULL))
> return;
> @@ -892,7 +947,7 @@ int evm_inode_init_security(struct inode *inode, struct inode *dir,
> if (!evm_protected_xattrs)
> return -EOPNOTSUPP;
>
> - evm_xattr = xattr;
> + evm_xattr = xattrs + integrity_blob_sizes.lbs_xattr;
Please don't do this inline. Convention is to use a function,
intergrity_xattrs() for this.
>
> xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
> if (!xattr_data)
> @@ -952,4 +1007,23 @@ static int __init init_evm(void)
> return error;
> }
>
> +static struct security_hook_list evm_hooks[] __lsm_ro_after_init = {
> + LSM_HOOK_INIT(inode_setattr, evm_inode_setattr),
> + LSM_HOOK_INIT(inode_post_setattr, evm_inode_post_setattr),
> + LSM_HOOK_INIT(inode_setxattr, evm_inode_setxattr),
> + LSM_HOOK_INIT(inode_set_acl, evm_inode_set_acl),
> + LSM_HOOK_INIT(inode_post_set_acl, evm_inode_post_set_acl),
> + LSM_HOOK_INIT(inode_remove_acl, evm_inode_remove_acl),
> + LSM_HOOK_INIT(inode_post_remove_acl, evm_inode_post_remove_acl),
> + LSM_HOOK_INIT(inode_post_setxattr, evm_inode_post_setxattr),
> + LSM_HOOK_INIT(inode_removexattr, evm_inode_removexattr),
> + LSM_HOOK_INIT(inode_post_removexattr, evm_inode_post_removexattr),
> + LSM_HOOK_INIT(inode_init_security, evm_inode_init_security),
> +};
> +
> +void __init init_evm_lsm(void)
> +{
> + security_add_hooks(evm_hooks, ARRAY_SIZE(evm_hooks), "integrity");
> +}
> +
> late_initcall(init_evm);
> diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> index bbadf974b31..952d5ea4e18 100644
> --- a/security/integrity/iint.c
> +++ b/security/integrity/iint.c
> @@ -179,12 +179,19 @@ static int __init integrity_lsm_init(void)
> 0, SLAB_PANIC, init_once);
>
> init_ima_lsm();
> + init_evm_lsm();
> return 0;
> }
> +
> +struct lsm_blob_sizes integrity_blob_sizes __lsm_ro_after_init = {
> + .lbs_xattr = 1,
Really? 1 byte? Don't even think of storing number of elements in lbs_xattr.
The linux_blob_size structure contains sizes of blobs, not number of elements.
> +};
> +
> DEFINE_LSM(integrity) = {
> .name = "integrity",
> .init = integrity_lsm_init,
> .order = LSM_ORDER_LAST,
> + .blobs = &integrity_blob_sizes,
> };
>
> /*
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index c72d375a356..76e7eda6651 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -188,6 +188,7 @@ int integrity_kernel_read(struct file *file, loff_t offset,
> #define INTEGRITY_KEYRING_MAX 4
>
> extern struct dentry *integrity_dir;
> +extern struct lsm_blob_sizes integrity_blob_sizes;
>
> struct modsig;
>
> @@ -199,6 +200,14 @@ static inline void __init init_ima_lsm(void)
> }
> #endif
>
> +#ifdef CONFIG_EVM
> +void __init init_evm_lsm(void);
> +#else
> +static inline void __init init_evm_lsm(void)
> +{
> +}
> +#endif
> +
> #ifdef CONFIG_INTEGRITY_SIGNATURE
>
> int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
> diff --git a/security/security.c b/security/security.c
> index 9bc6a4ef758..74abf04feef 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -20,13 +20,13 @@
> #include <linux/kernel_read_file.h>
> #include <linux/lsm_hooks.h>
> #include <linux/integrity.h>
> -#include <linux/evm.h>
> #include <linux/fsnotify.h>
> #include <linux/mman.h>
> #include <linux/mount.h>
> #include <linux/personality.h>
> #include <linux/backing-dev.h>
> #include <linux/string.h>
> +#include <linux/xattr.h>
> #include <linux/msg.h>
> #include <net/flow.h>
>
> @@ -1662,8 +1662,8 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> if (!initxattrs)
> return call_int_hook(inode_init_security, -EOPNOTSUPP, inode,
> dir, qstr, NULL);
> - /* Allocate +1 for EVM and +1 as terminator. */
> - new_xattrs = kcalloc(blob_sizes.lbs_xattr + 2, sizeof(*new_xattrs),
> + /* Allocate +1 for terminator. */
> + new_xattrs = kcalloc(blob_sizes.lbs_xattr + 1, sizeof(*new_xattrs),
> GFP_NOFS);
> if (!new_xattrs)
> return -ENOMEM;
> @@ -1699,9 +1699,6 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> if (!num_filled_xattrs)
> goto out;
>
> - ret = evm_inode_init_security(inode, dir, qstr, new_xattrs);
> - if (ret && ret != -EOPNOTSUPP)
> - goto out;
> ret = initxattrs(inode, new_xattrs, fs_data);
> out:
> for (xattr = new_xattrs; xattr->value != NULL; xattr++)
> @@ -2201,14 +2198,9 @@ int security_inode_permission(struct inode *inode, int mask)
> int security_inode_setattr(struct mnt_idmap *idmap,
> struct dentry *dentry, struct iattr *attr)
> {
> - int ret;
> -
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return 0;
> - ret = call_int_hook(inode_setattr, 0, idmap, dentry, attr);
> - if (ret)
> - return ret;
> - return evm_inode_setattr(idmap, dentry, attr);
> + return call_int_hook(inode_setattr, 0, idmap, dentry, attr);
> }
> EXPORT_SYMBOL_GPL(security_inode_setattr);
>
> @@ -2272,9 +2264,7 @@ int security_inode_setxattr(struct mnt_idmap *idmap,
>
> if (ret == 1)
> ret = cap_inode_setxattr(dentry, name, value, size, flags);
> - if (ret)
> - return ret;
> - return evm_inode_setxattr(idmap, dentry, name, value, size, flags);
> + return ret;
> }
>
> /**
> @@ -2293,15 +2283,10 @@ int security_inode_set_acl(struct mnt_idmap *idmap,
> struct dentry *dentry, const char *acl_name,
> struct posix_acl *kacl)
> {
> - int ret;
> -
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return 0;
> - ret = call_int_hook(inode_set_acl, 0, idmap, dentry, acl_name,
> - kacl);
> - if (ret)
> - return ret;
> - return evm_inode_set_acl(idmap, dentry, acl_name, kacl);
> + return call_int_hook(inode_set_acl, 0, idmap, dentry, acl_name,
> + kacl);
> }
>
> /**
> @@ -2354,14 +2339,9 @@ int security_inode_get_acl(struct mnt_idmap *idmap,
> int security_inode_remove_acl(struct mnt_idmap *idmap,
> struct dentry *dentry, const char *acl_name)
> {
> - int ret;
> -
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return 0;
> - ret = call_int_hook(inode_remove_acl, 0, idmap, dentry, acl_name);
> - if (ret)
> - return ret;
> - return evm_inode_remove_acl(idmap, dentry, acl_name);
> + return call_int_hook(inode_remove_acl, 0, idmap, dentry, acl_name);
> }
>
> /**
> @@ -2397,7 +2377,6 @@ 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);
> - evm_inode_post_setxattr(dentry, name, value, size, flags);
> }
>
> /**
> @@ -2458,9 +2437,7 @@ int security_inode_removexattr(struct mnt_idmap *idmap,
> ret = call_int_hook(inode_removexattr, 1, idmap, dentry, name);
> if (ret == 1)
> ret = cap_inode_removexattr(idmap, dentry, name);
> - if (ret)
> - return ret;
> - return evm_inode_removexattr(idmap, dentry, name);
> + return ret;
> }
>
> /**
