From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- security/loadpin/loadpin.c | 442 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 442 insertions(+) create mode 100644 security/loadpin/loadpin.c (limited to 'security/loadpin/loadpin.c') diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c new file mode 100644 index 000000000..f71861f98 --- /dev/null +++ b/security/loadpin/loadpin.c @@ -0,0 +1,442 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Module and Firmware Pinning Security Module + * + * Copyright 2011-2016 Google Inc. + * + * Author: Kees Cook + */ + +#define pr_fmt(fmt) "LoadPin: " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include /* current */ +#include +#include +#include +#include + +#define VERITY_DIGEST_FILE_HEADER "# LOADPIN_TRUSTED_VERITY_ROOT_DIGESTS" + +static void report_load(const char *origin, struct file *file, char *operation) +{ + char *cmdline, *pathname; + + pathname = kstrdup_quotable_file(file, GFP_KERNEL); + cmdline = kstrdup_quotable_cmdline(current, GFP_KERNEL); + + pr_notice("%s %s obj=%s%s%s pid=%d cmdline=%s%s%s\n", + origin, operation, + (pathname && pathname[0] != '<') ? "\"" : "", + pathname, + (pathname && pathname[0] != '<') ? "\"" : "", + task_pid_nr(current), + cmdline ? "\"" : "", cmdline, cmdline ? "\"" : ""); + + kfree(cmdline); + kfree(pathname); +} + +static int enforce = IS_ENABLED(CONFIG_SECURITY_LOADPIN_ENFORCE); +static char *exclude_read_files[READING_MAX_ID]; +static int ignore_read_file_id[READING_MAX_ID] __ro_after_init; +static struct super_block *pinned_root; +static DEFINE_SPINLOCK(pinned_root_spinlock); +#ifdef CONFIG_SECURITY_LOADPIN_VERITY +static bool deny_reading_verity_digests; +#endif + +// initialized to false +static bool loadpin_root_writable; +#ifdef CONFIG_SYSCTL + +static int proc_handler_loadpin(const struct ctl_table *table, int dir, + void *buffer, size_t *lenp, loff_t *ppos) +{ + if (!loadpin_root_writable && SYSCTL_USER_TO_KERN(dir)) + return -EINVAL; + return proc_dointvec_minmax(table, dir, buffer, lenp, ppos); +} + +static const struct ctl_table loadpin_sysctl_table[] = { + { + .procname = "enforce", + .data = &enforce, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_handler_loadpin, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, +}; +#endif + +static void report_writable(struct super_block *mnt_sb, bool writable) +{ + if (mnt_sb->s_bdev) { + pr_info("%pg (%u:%u): %s\n", mnt_sb->s_bdev, + MAJOR(mnt_sb->s_bdev->bd_dev), + MINOR(mnt_sb->s_bdev->bd_dev), + writable ? "writable" : "read-only"); + } else + pr_info("mnt_sb lacks block device, treating as: writable\n"); + + if (!writable) + pr_info("load pinning engaged.\n"); +} + +/* + * This must be called after early kernel init, since then the rootdev + * is available. + */ +static bool sb_is_writable(struct super_block *mnt_sb) +{ + bool writable = true; + + if (mnt_sb->s_bdev) + writable = !bdev_read_only(mnt_sb->s_bdev); + + return writable; +} + +static void loadpin_sb_free_security(struct super_block *mnt_sb) +{ + /* + * When unmounting the filesystem we were using for load + * pinning, we acknowledge the superblock release, but make sure + * no other modules or firmware can be loaded when we are in + * enforcing mode. Otherwise, allow the root to be reestablished. + */ + if (!IS_ERR_OR_NULL(pinned_root) && mnt_sb == pinned_root) { + if (enforce) { + pinned_root = ERR_PTR(-EIO); + pr_info("umount pinned fs: refusing further loads\n"); + } else { + pinned_root = NULL; + } + } +} + +static int loadpin_check(struct file *file, enum kernel_read_file_id id) +{ + struct super_block *load_root; + const char *origin = kernel_read_file_id_str(id); + bool first_root_pin = false; + + /* If the file id is excluded, ignore the pinning. */ + if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) && + ignore_read_file_id[id]) { + report_load(origin, file, "pinning-excluded"); + return 0; + } + + /* This handles the older init_module API that has a NULL file. */ + if (!file) { + if (!enforce) { + report_load(origin, NULL, "old-api-pinning-ignored"); + return 0; + } + + report_load(origin, NULL, "old-api-denied"); + return -EPERM; + } + + load_root = file->f_path.mnt->mnt_sb; + + /* First loaded module/firmware defines the root for all others. */ + spin_lock(&pinned_root_spinlock); + /* + * pinned_root is only NULL at startup or when the pinned root has + * been unmounted while we are not in enforcing mode. Otherwise, it + * is either a valid reference, or an ERR_PTR. + */ + if (!pinned_root) { + pinned_root = load_root; + first_root_pin = true; + } + spin_unlock(&pinned_root_spinlock); + + if (first_root_pin) { + loadpin_root_writable = sb_is_writable(pinned_root); + report_writable(pinned_root, loadpin_root_writable); + report_load(origin, file, "pinned"); + } + + if (IS_ERR_OR_NULL(pinned_root) || + ((load_root != pinned_root) && !dm_verity_loadpin_is_bdev_trusted(load_root->s_bdev))) { + if (unlikely(!enforce)) { + report_load(origin, file, "pinning-ignored"); + return 0; + } + + report_load(origin, file, "denied"); + return -EPERM; + } + + return 0; +} + +static int loadpin_read_file(struct file *file, enum kernel_read_file_id id, + bool contents) +{ + /* + * LoadPin only cares about the _origin_ of a file, not its + * contents, so we can ignore the "are full contents available" + * argument here. + */ + return loadpin_check(file, id); +} + +static int loadpin_load_data(enum kernel_load_data_id id, bool contents) +{ + /* + * LoadPin only cares about the _origin_ of a file, not its + * contents, so a NULL file is passed, and we can ignore the + * state of "contents". + */ + return loadpin_check(NULL, (enum kernel_read_file_id) id); +} + +static const struct lsm_id loadpin_lsmid = { + .name = "loadpin", + .id = LSM_ID_LOADPIN, +}; + +static struct security_hook_list loadpin_hooks[] __ro_after_init = { + LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security), + LSM_HOOK_INIT(kernel_read_file, loadpin_read_file), + LSM_HOOK_INIT(kernel_load_data, loadpin_load_data), +}; + +static void __init parse_exclude(void) +{ + int i, j; + char *cur; + + /* + * Make sure all the arrays stay within expected sizes. This + * is slightly weird because kernel_read_file_str[] includes + * READING_MAX_ID, which isn't actually meaningful here. + */ + BUILD_BUG_ON(ARRAY_SIZE(exclude_read_files) != + ARRAY_SIZE(ignore_read_file_id)); + BUILD_BUG_ON(ARRAY_SIZE(kernel_read_file_str) < + ARRAY_SIZE(ignore_read_file_id)); + + for (i = 0; i < ARRAY_SIZE(exclude_read_files); i++) { + cur = exclude_read_files[i]; + if (!cur) + break; + if (*cur == '\0') + continue; + + for (j = 0; j < ARRAY_SIZE(ignore_read_file_id); j++) { + if (strcmp(cur, kernel_read_file_str[j]) == 0) { + pr_info("excluding: %s\n", + kernel_read_file_str[j]); + ignore_read_file_id[j] = 1; + /* + * Can not break, because one read_file_str + * may map to more than on read_file_id. + */ + } + } + } +} + +static int __init loadpin_init(void) +{ + pr_info("ready to pin (currently %senforcing)\n", + enforce ? "" : "not "); + parse_exclude(); +#ifdef CONFIG_SYSCTL + if (!register_sysctl("kernel/loadpin", loadpin_sysctl_table)) + pr_notice("sysctl registration failed!\n"); +#endif + security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), + &loadpin_lsmid); + + return 0; +} + +#ifdef CONFIG_SECURITY_LOADPIN_VERITY + +enum loadpin_securityfs_interface_index { + LOADPIN_DM_VERITY, +}; + +static int read_trusted_verity_root_digests(unsigned int fd) +{ + void *data; + int rc; + char *p, *d; + + if (deny_reading_verity_digests) + return -EPERM; + + /* The list of trusted root digests can only be set up once */ + if (!list_empty(&dm_verity_loadpin_trusted_root_digests)) + return -EPERM; + + CLASS(fd, f)(fd); + if (fd_empty(f)) + return -EINVAL; + + data = kzalloc(SZ_4K, GFP_KERNEL); + if (!data) { + rc = -ENOMEM; + goto err; + } + + rc = kernel_read_file(fd_file(f), 0, (void **)&data, SZ_4K - 1, NULL, READING_POLICY); + if (rc < 0) + goto err; + + p = data; + p[rc] = '\0'; + p = strim(p); + + p = strim(data); + while ((d = strsep(&p, "\n")) != NULL) { + int len; + struct dm_verity_loadpin_trusted_root_digest *trd; + + if (d == data) { + /* first line, validate header */ + if (strcmp(d, VERITY_DIGEST_FILE_HEADER)) { + rc = -EPROTO; + goto err; + } + + continue; + } + + len = strlen(d); + + if (len % 2) { + rc = -EPROTO; + goto err; + } + + len /= 2; + + trd = kzalloc_flex(*trd, data, len); + if (!trd) { + rc = -ENOMEM; + goto err; + } + trd->len = len; + + if (hex2bin(trd->data, d, len)) { + kfree(trd); + rc = -EPROTO; + goto err; + } + + list_add_tail(&trd->node, &dm_verity_loadpin_trusted_root_digests); + } + + if (list_empty(&dm_verity_loadpin_trusted_root_digests)) { + rc = -EPROTO; + goto err; + } + + kfree(data); + + return 0; + +err: + kfree(data); + + /* any failure in loading/parsing invalidates the entire list */ + { + struct dm_verity_loadpin_trusted_root_digest *trd, *tmp; + + list_for_each_entry_safe(trd, tmp, &dm_verity_loadpin_trusted_root_digests, node) { + list_del(&trd->node); + kfree(trd); + } + } + + /* disallow further attempts after reading a corrupt/invalid file */ + deny_reading_verity_digests = true; + + return rc; +} + +/******************************** securityfs ********************************/ + +static long dm_verity_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) +{ + void __user *uarg = (void __user *)arg; + unsigned int fd; + + switch (cmd) { + case LOADPIN_IOC_SET_TRUSTED_VERITY_DIGESTS: + if (copy_from_user(&fd, uarg, sizeof(fd))) + return -EFAULT; + + return read_trusted_verity_root_digests(fd); + + default: + return -EINVAL; + } +} + +static const struct file_operations loadpin_dm_verity_ops = { + .unlocked_ioctl = dm_verity_ioctl, + .compat_ioctl = compat_ptr_ioctl, +}; + +/** + * init_loadpin_securityfs - create the securityfs directory for LoadPin + * + * We can not put this method normally under the loadpin_init() code path since + * the security subsystem gets initialized before the vfs caches. + * + * Returns 0 if the securityfs directory creation was successful. + */ +static int __init init_loadpin_securityfs(void) +{ + struct dentry *loadpin_dir, *dentry; + + loadpin_dir = securityfs_create_dir("loadpin", NULL); + if (IS_ERR(loadpin_dir)) { + pr_err("LoadPin: could not create securityfs dir: %ld\n", + PTR_ERR(loadpin_dir)); + return PTR_ERR(loadpin_dir); + } + + dentry = securityfs_create_file("dm-verity", 0600, loadpin_dir, + (void *)LOADPIN_DM_VERITY, &loadpin_dm_verity_ops); + if (IS_ERR(dentry)) { + pr_err("LoadPin: could not create securityfs entry 'dm-verity': %ld\n", + PTR_ERR(dentry)); + return PTR_ERR(dentry); + } + + return 0; +} + +#endif /* CONFIG_SECURITY_LOADPIN_VERITY */ + +DEFINE_LSM(loadpin) = { + .id = &loadpin_lsmid, + .init = loadpin_init, +#ifdef CONFIG_SECURITY_LOADPIN_VERITY + .initcall_fs = init_loadpin_securityfs, +#endif /* CONFIG_SECURITY_LOADPIN_VERITY */ +}; + +/* Should not be mutable after boot, so not listed in sysfs (perm == 0). */ +module_param(enforce, int, 0); +MODULE_PARM_DESC(enforce, "Enforce module/firmware pinning"); +module_param_array_named(exclude, exclude_read_files, charp, NULL, 0); +MODULE_PARM_DESC(exclude, "Exclude pinning specific read file types"); -- cgit v1.3.1