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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-12 00:42:44 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-12 00:42:44 +0300
commitc079512aad9718c12c6bb1b661880b15a73dfd69 (patch)
treeb8cb70b4d40102bb806287fe7592b713e032a16c
parent6b44fccdb8cdcc7c1df522529307566aa89a4ab1 (diff)
parent0ff9848067b7b950a4ed70de7f5028600a2157e3 (diff)
downloadlinux-c079512aad9718c12c6bb1b661880b15a73dfd69.tar.xz
Merge tag 'loadpin-v5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull security/loadpin updates from Kees Cook: - Allow exclusion of specific file types (Ke Wu) * tag 'loadpin-v5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: security/loadpin: Allow to exclude specific file types
-rw-r--r--Documentation/admin-guide/LSM/LoadPin.rst10
-rw-r--r--security/loadpin/loadpin.c48
2 files changed, 58 insertions, 0 deletions
diff --git a/Documentation/admin-guide/LSM/LoadPin.rst b/Documentation/admin-guide/LSM/LoadPin.rst
index 32070762d24c..716ad9b23c9a 100644
--- a/Documentation/admin-guide/LSM/LoadPin.rst
+++ b/Documentation/admin-guide/LSM/LoadPin.rst
@@ -19,3 +19,13 @@ block device backing the filesystem is not read-only, a sysctl is
created to toggle pinning: ``/proc/sys/kernel/loadpin/enabled``. (Having
a mutable filesystem means pinning is mutable too, but having the
sysctl allows for easy testing on systems with a mutable filesystem.)
+
+It's also possible to exclude specific file types from LoadPin using kernel
+command line option "``loadpin.exclude``". By default, all files are
+included, but they can be excluded using kernel command line option such
+as "``loadpin.exclude=kernel-module,kexec-image``". This allows to use
+different mechanisms such as ``CONFIG_MODULE_SIG`` and
+``CONFIG_KEXEC_VERIFY_SIG`` to verify kernel module and kernel image while
+still use LoadPin to protect the integrity of other files kernel loads. The
+full list of valid file types can be found in ``kernel_read_file_str``
+defined in ``include/linux/fs.h``.
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
index 79131efa9634..81519c804888 100644
--- a/security/loadpin/loadpin.c
+++ b/security/loadpin/loadpin.c
@@ -37,6 +37,8 @@ static void report_load(const char *origin, struct file *file, char *operation)
}
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);
@@ -121,6 +123,13 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
struct super_block *load_root;
const char *origin = kernel_read_file_id_str(id);
+ /* 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) {
@@ -179,10 +188,47 @@ static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
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();
security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
return 0;
}
@@ -195,3 +241,5 @@ DEFINE_LSM(loadpin) = {
/* 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");