Commit 99bd9956 authored by Aaron Tomlin's avatar Aaron Tomlin Committed by Luis Chamberlain

module: Introduce module unload taint tracking

Currently, only the initial module that tainted the kernel is
recorded e.g. when an out-of-tree module is loaded.

The purpose of this patch is to allow the kernel to maintain a record of
each unloaded module that taints the kernel. So, in addition to
displaying a list of linked modules (see print_modules()) e.g. in the
event of a detected bad page, unloaded modules that carried a taint/or
taints are displayed too. A tainted module unload count is maintained.

The number of tracked modules is not fixed. This feature is disabled by
default.
Signed-off-by: default avatarAaron Tomlin <atomlin@redhat.com>
Signed-off-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
parent 6fb0538d
......@@ -2118,6 +2118,17 @@ config MODULE_FORCE_UNLOAD
rmmod). This is mainly for kernel developers and desperate users.
If unsure, say N.
config MODULE_UNLOAD_TAINT_TRACKING
bool "Tainted module unload tracking"
depends on MODULE_UNLOAD
default n
help
This option allows you to maintain a record of each unloaded
module that tainted the kernel. In addition to displaying a
list of linked (or loaded) modules e.g. on detection of a bad
page (see bad_page()), the aforementioned details are also
shown. If unsure, say N.
config MODVERSIONS
bool "Module versioning support"
help
......
......@@ -18,3 +18,4 @@ obj-$(CONFIG_PROC_FS) += procfs.o
obj-$(CONFIG_SYSFS) += sysfs.o
obj-$(CONFIG_KGDB_KDB) += kdb.o
obj-$(CONFIG_MODVERSIONS) += version.o
obj-$(CONFIG_MODULE_UNLOAD_TAINT_TRACKING) += tracking.o
......@@ -145,6 +145,27 @@ static inline bool set_livepatch_module(struct module *mod)
#endif
}
#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING
struct mod_unload_taint {
struct list_head list;
char name[MODULE_NAME_LEN];
unsigned long taints;
u64 count;
};
int try_add_tainted_module(struct module *mod);
void print_unloaded_tainted_modules(void);
#else /* !CONFIG_MODULE_UNLOAD_TAINT_TRACKING */
static inline int try_add_tainted_module(struct module *mod)
{
return 0;
}
static inline void print_unloaded_tainted_modules(void)
{
}
#endif /* CONFIG_MODULE_UNLOAD_TAINT_TRACKING */
#ifdef CONFIG_MODULE_DECOMPRESS
int module_decompress(struct load_info *info, const void *buf, size_t size);
void module_decompress_cleanup(struct load_info *info);
......
......@@ -1190,6 +1190,9 @@ static void free_module(struct module *mod)
module_bug_cleanup(mod);
/* Wait for RCU-sched synchronizing before releasing mod->list and buglist. */
synchronize_rcu();
if (try_add_tainted_module(mod))
pr_err("%s: adding tainted module to the unloaded tainted modules list failed.\n",
mod->name);
mutex_unlock(&module_mutex);
/* Clean up CFI for the module. */
......@@ -3125,6 +3128,8 @@ void print_modules(void)
continue;
pr_cont(" %s%s", mod->name, module_flags(mod, buf));
}
print_unloaded_tainted_modules();
preempt_enable();
if (last_unloaded_module[0])
pr_cont(" [last unloaded: %s]", last_unloaded_module);
......
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Module taint unload tracking support
*
* Copyright (C) 2022 Aaron Tomlin
*/
#include <linux/module.h>
#include <linux/string.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include "internal.h"
static LIST_HEAD(unloaded_tainted_modules);
int try_add_tainted_module(struct module *mod)
{
struct mod_unload_taint *mod_taint;
module_assert_mutex_or_preempt();
list_for_each_entry_rcu(mod_taint, &unloaded_tainted_modules, list,
lockdep_is_held(&module_mutex)) {
if (!strcmp(mod_taint->name, mod->name) &&
mod_taint->taints & mod->taints) {
mod_taint->count++;
goto out;
}
}
mod_taint = kmalloc(sizeof(*mod_taint), GFP_KERNEL);
if (unlikely(!mod_taint))
return -ENOMEM;
strscpy(mod_taint->name, mod->name, MODULE_NAME_LEN);
mod_taint->taints = mod->taints;
list_add_rcu(&mod_taint->list, &unloaded_tainted_modules);
mod_taint->count = 1;
out:
return 0;
}
void print_unloaded_tainted_modules(void)
{
struct mod_unload_taint *mod_taint;
char buf[MODULE_FLAGS_BUF_SIZE];
if (!list_empty(&unloaded_tainted_modules)) {
printk(KERN_DEFAULT "Unloaded tainted modules:");
list_for_each_entry_rcu(mod_taint, &unloaded_tainted_modules,
list) {
size_t l;
l = module_flags_taint(mod_taint->taints, buf);
buf[l++] = '\0';
pr_cont(" %s(%s):%llu", mod_taint->name, buf,
mod_taint->count);
}
}
}
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