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    Subject[PATCH v4 8/8] module: replace the existing LSM hook in init_module
    Date
    Both the init_module and finit_module syscalls call either directly
    or indirectly the security_kernel_read_file LSM hook. This patch
    replaces the direct call in init_module with a call to the new
    security_kernel_load_data hook and makes the corresponding changes in
    SELinux and IMA.

    Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
    Cc: Jeff Vander Stoep <jeffv@google.com>
    Cc: Paul Moore <paul@paul-moore.com>
    Cc: Casey Schaufler <casey@schaufler-ca.com>
    ---
    kernel/module.c | 2 +-
    security/integrity/ima/ima_main.c | 24 ++++++++++--------------
    security/selinux/hooks.c | 26 ++++++++++++++++++++------
    3 files changed, 31 insertions(+), 21 deletions(-)

    diff --git a/kernel/module.c b/kernel/module.c
    index ce8066b88178..b97c642b5b4d 100644
    --- a/kernel/module.c
    +++ b/kernel/module.c
    @@ -2879,7 +2879,7 @@ static int copy_module_from_user(const void __user *umod, unsigned long len,
    if (info->len < sizeof(*(info->hdr)))
    return -ENOEXEC;

    - err = security_kernel_read_file(NULL, READING_MODULE);
    + err = security_kernel_load_data(LOADING_MODULE);
    if (err)
    return err;

    diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
    index 3dae605a1604..0ff1d8152f6e 100644
    --- a/security/integrity/ima/ima_main.c
    +++ b/security/integrity/ima/ima_main.c
    @@ -441,17 +441,6 @@ static int read_idmap[READING_MAX_ID] = {
    */
    int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
    {
    - bool sig_enforce = is_module_sig_enforced();
    -
    - if (!file && read_id == READING_MODULE) {
    - if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
    - (ima_appraise & IMA_APPRAISE_ENFORCE)) {
    - pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
    - return -EACCES; /* INTEGRITY_UNKNOWN */
    - }
    - return 0; /* We rely on module signature checking */
    - }
    -
    if (read_id == READING_FIRMWARE_PREALLOC_BUFFER) {
    if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
    @@ -490,9 +479,6 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
    return 0;
    }

    - if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
    - return 0;
    -
    /* permit signed certs */
    if (!file && read_id == READING_X509_CERTIFICATE)
    return 0;
    @@ -521,6 +507,8 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
    */
    int ima_load_data(enum kernel_load_data_id id)
    {
    + bool sig_enforce;
    +
    if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
    return 0;

    @@ -536,6 +524,14 @@ int ima_load_data(enum kernel_load_data_id id)
    pr_err("Prevent firmware sysfs fallback loading.\n");
    return -EACCES; /* INTEGRITY_UNKNOWN */
    }
    + break;
    + case LOADING_MODULE:
    + sig_enforce = is_module_sig_enforced();
    +
    + if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES)) {
    + pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
    + return -EACCES; /* INTEGRITY_UNKNOWN */
    + }
    default:
    break;
    }
    diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
    index 02ebd1585eaf..e02186470fc5 100644
    --- a/security/selinux/hooks.c
    +++ b/security/selinux/hooks.c
    @@ -4018,12 +4018,6 @@ static int selinux_kernel_module_from_file(struct file *file)
    u32 sid = current_sid();
    int rc;

    - /* init_module */
    - if (file == NULL)
    - return avc_has_perm(&selinux_state,
    - sid, sid, SECCLASS_SYSTEM,
    - SYSTEM__MODULE_LOAD, NULL);
    -
    /* finit_module */

    ad.type = LSM_AUDIT_DATA_FILE;
    @@ -4043,6 +4037,25 @@ static int selinux_kernel_module_from_file(struct file *file)
    SYSTEM__MODULE_LOAD, &ad);
    }

    +static int selinux_kernel_load_data(enum kernel_load_data_id id)
    +{
    + u32 sid;
    + int rc = 0;
    +
    + switch (id) {
    + case LOADING_MODULE:
    + sid = current_sid();
    +
    + /* init_module */
    + return avc_has_perm(&selinux_state, sid, sid, SECCLASS_SYSTEM,
    + SYSTEM__MODULE_LOAD, NULL);
    + default:
    + break;
    + }
    +
    + return rc;
    +}
    +
    static int selinux_kernel_read_file(struct file *file,
    enum kernel_read_file_id id)
    {
    @@ -6950,6 +6963,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
    LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as),
    LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as),
    LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request),
    + LSM_HOOK_INIT(kernel_load_data, selinux_kernel_load_data),
    LSM_HOOK_INIT(kernel_read_file, selinux_kernel_read_file),
    LSM_HOOK_INIT(task_setpgid, selinux_task_setpgid),
    LSM_HOOK_INIT(task_getpgid, selinux_task_getpgid),
    --
    2.7.5
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