* [RFC PATCH v2 0/2] module: Introduce module unload taint tracking
@ 2022-04-19 15:03 Aaron Tomlin
2022-04-19 15:03 ` [RFC PATCH v2 1/2] module: Make module_flags_taint() accept a module's taints bitmap directly Aaron Tomlin
2022-04-19 15:03 ` [RFC PATCH v2 2/2] module: Introduce module unload taint tracking Aaron Tomlin
0 siblings, 2 replies; 3+ messages in thread
From: Aaron Tomlin @ 2022-04-19 15:03 UTC (permalink / raw)
To: mcgrof
Cc: cl, pmladek, mbenes, christophe.leroy, akpm, linux-kernel,
linux-modules, atomlin, ghalat
Hi Luis,
This is based on the latest mcgrof/modules-next branch. I have decided
still to use RCU even though no entry is ever removed from the unloaded
tainted modules list. That being said, if I understand correctly, it is not
safe in some instances to use 'module_mutex' in print_modules(). So instead
we disable preemption to ensure list traversal with concurrent list
manipulation e.g. list_add_rcu(), is safe too.
Please let me know your thoughts.
Aaron Tomlin (2):
module: Make module_flags_taint() accept a module's taints bitmap
directly
module: Introduce module unload taint tracking
init/Kconfig | 11 +++++++
kernel/module/main.c | 76 +++++++++++++++++++++++++++++++++++++++++---
2 files changed, 83 insertions(+), 4 deletions(-)
base-commit: eeaec7801c421e17edda6e45a32d4a5596b633da
--
2.34.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* [RFC PATCH v2 1/2] module: Make module_flags_taint() accept a module's taints bitmap directly
2022-04-19 15:03 [RFC PATCH v2 0/2] module: Introduce module unload taint tracking Aaron Tomlin
@ 2022-04-19 15:03 ` Aaron Tomlin
2022-04-19 15:03 ` [RFC PATCH v2 2/2] module: Introduce module unload taint tracking Aaron Tomlin
1 sibling, 0 replies; 3+ messages in thread
From: Aaron Tomlin @ 2022-04-19 15:03 UTC (permalink / raw)
To: mcgrof
Cc: cl, pmladek, mbenes, christophe.leroy, akpm, linux-kernel,
linux-modules, atomlin, ghalat
No functional change.
The purpose of this patch is to modify module_flags_taint() to accept a
module's taints bitmap as a parameter and modifies all users accordingly.
This is in preparation for module unload taint tracking support.
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
---
kernel/module/main.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 05a42d8fcd7a..ea78cec316dd 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -890,13 +890,13 @@ static inline int module_unload_init(struct module *mod)
}
#endif /* CONFIG_MODULE_UNLOAD */
-static size_t module_flags_taint(struct module *mod, char *buf)
+static size_t module_flags_taint(unsigned long taints, char *buf)
{
size_t l = 0;
int i;
for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
- if (taint_flags[i].module && test_bit(i, &mod->taints))
+ if (taint_flags[i].module && test_bit(i, &taints))
buf[l++] = taint_flags[i].c_true;
}
@@ -974,7 +974,7 @@ static ssize_t show_taint(struct module_attribute *mattr,
{
size_t l;
- l = module_flags_taint(mk->mod, buffer);
+ l = module_flags_taint(mk->mod->taints, buffer);
buffer[l++] = '\n';
return l;
}
@@ -2993,7 +2993,7 @@ char *module_flags(struct module *mod, char *buf)
mod->state == MODULE_STATE_GOING ||
mod->state == MODULE_STATE_COMING) {
buf[bx++] = '(';
- bx += module_flags_taint(mod, buf + bx);
+ bx += module_flags_taint(mod->taints, buf + bx);
/* Show a - for module-is-being-unloaded */
if (mod->state == MODULE_STATE_GOING)
buf[bx++] = '-';
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [RFC PATCH v2 2/2] module: Introduce module unload taint tracking
2022-04-19 15:03 [RFC PATCH v2 0/2] module: Introduce module unload taint tracking Aaron Tomlin
2022-04-19 15:03 ` [RFC PATCH v2 1/2] module: Make module_flags_taint() accept a module's taints bitmap directly Aaron Tomlin
@ 2022-04-19 15:03 ` Aaron Tomlin
1 sibling, 0 replies; 3+ messages in thread
From: Aaron Tomlin @ 2022-04-19 15:03 UTC (permalink / raw)
To: mcgrof
Cc: cl, pmladek, mbenes, christophe.leroy, akpm, linux-kernel,
linux-modules, atomlin, ghalat
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. If a previously unloaded module with a
taint/or tains is loaded once again and then a count will be shown
accordingly.
The number of tracked modules is not fixed. This feature is disabled by
default.
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
---
init/Kconfig | 11 +++++++
kernel/module/main.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 79 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index ddcbefe535e9..6b30210f787d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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
diff --git a/kernel/module/main.c b/kernel/module/main.c
index ea78cec316dd..0f7df9ac25ce 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -68,6 +68,16 @@
*/
DEFINE_MUTEX(module_mutex);
LIST_HEAD(modules);
+#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING
+static LIST_HEAD(unloaded_tainted_modules);
+
+struct mod_unload_taint {
+ struct list_head list;
+ char name[MODULE_NAME_LEN];
+ unsigned long taints;
+ u64 count;
+};
+#endif
/* Work queue for freeing init sections in success case */
static void do_free_init(struct work_struct *w);
@@ -150,6 +160,42 @@ int unregister_module_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL(unregister_module_notifier);
+#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING
+static 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)) {
+ size_t len = strlen(mod_taint->name);
+
+ if (len == strlen(mod->name) && !memcmp(mod_taint->name, mod->name, len) &&
+ mod_taint->taints & mod->taints) {
+ mod_taint->count++;
+ goto out;
+ }
+ }
+
+ mod_taint = kmalloc(sizeof(*mod_taint), GFP_KERNEL);
+ if (unlikely(!mod_taint))
+ return -ENOMEM;
+ strlcpy(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 = 0;
+out:
+ return 0;
+}
+#else /* MODULE_UNLOAD_TAINT_TRACKING */
+static int try_add_tainted_module(struct module *mod)
+{
+ return 0;
+}
+#endif
+
/*
* We require a truly strong try_module_get(): 0 means success.
* Otherwise an error is returned due to ongoing or failed
@@ -1201,6 +1247,9 @@ 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. */
@@ -3126,6 +3175,9 @@ struct module *__module_text_address(unsigned long addr)
void print_modules(void)
{
struct module *mod;
+#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING
+ struct mod_unload_taint *mod_taint;
+#endif
char buf[MODULE_FLAGS_BUF_SIZE];
printk(KERN_DEFAULT "Modules linked in:");
@@ -3136,6 +3188,22 @@ void print_modules(void)
continue;
pr_cont(" %s%s", mod->name, module_flags(mod, buf));
}
+#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING
+ if (!list_empty(&unloaded_tainted_modules)) {
+ printk(KERN_DEFAULT "\nUnloaded 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)%s", mod_taint->name, buf,
+ mod_taint->count ? ":" : "");
+ if (mod_taint->count)
+ pr_cont("%llu", mod_taint->count);
+ }
+#endif
+ }
preempt_enable();
if (last_unloaded_module[0])
pr_cont(" [last unloaded: %s]", last_unloaded_module);
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-04-19 15:03 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-19 15:03 [RFC PATCH v2 0/2] module: Introduce module unload taint tracking Aaron Tomlin
2022-04-19 15:03 ` [RFC PATCH v2 1/2] module: Make module_flags_taint() accept a module's taints bitmap directly Aaron Tomlin
2022-04-19 15:03 ` [RFC PATCH v2 2/2] module: Introduce module unload taint tracking Aaron Tomlin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).