Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching

Pull livepatching fix from Jiri Kosina:
 "Shadow variable API list_head initialization fix from Petr Mladek"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching:
  livepatch: Allow to call a custom callback when freeing shadow variables
  livepatch: Initialize shadow variables safely by a custom callback
This commit is contained in:
Linus Torvalds 2018-04-20 08:51:55 -07:00
commit 41e3bef52e
5 changed files with 163 additions and 81 deletions

View File

@ -34,9 +34,13 @@ meta-data and shadow-data:
- data[] - storage for shadow data
It is important to note that the klp_shadow_alloc() and
klp_shadow_get_or_alloc() calls, described below, store a *copy* of the
data that the functions are provided. Callers should provide whatever
mutual exclusion is required of the shadow data.
klp_shadow_get_or_alloc() are zeroing the variable by default.
They also allow to call a custom constructor function when a non-zero
value is needed. Callers should provide whatever mutual exclusion
is required.
Note that the constructor is called under klp_shadow_lock spinlock. It allows
to do actions that can be done only once when a new variable is allocated.
* klp_shadow_get() - retrieve a shadow variable data pointer
- search hashtable for <obj, id> pair
@ -47,7 +51,7 @@ mutual exclusion is required of the shadow data.
- WARN and return NULL
- if <obj, id> doesn't already exist
- allocate a new shadow variable
- copy data into the new shadow variable
- initialize the variable using a custom constructor and data when provided
- add <obj, id> to the global hashtable
* klp_shadow_get_or_alloc() - get existing or alloc a new shadow variable
@ -56,16 +60,20 @@ mutual exclusion is required of the shadow data.
- return existing shadow variable
- if <obj, id> doesn't already exist
- allocate a new shadow variable
- copy data into the new shadow variable
- initialize the variable using a custom constructor and data when provided
- add <obj, id> pair to the global hashtable
* klp_shadow_free() - detach and free a <obj, id> shadow variable
- find and remove a <obj, id> reference from global hashtable
- if found, free shadow variable
- if found
- call destructor function if defined
- free shadow variable
* klp_shadow_free_all() - detach and free all <*, id> shadow variables
- find and remove any <*, id> references from global hashtable
- if found, free shadow variable
- if found
- call destructor function if defined
- free shadow variable
2. Use cases
@ -107,7 +115,8 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
sta = kzalloc(sizeof(*sta) + hw->sta_data_size, gfp);
/* Attach a corresponding shadow variable, then initialize it */
ps_lock = klp_shadow_alloc(sta, PS_LOCK, NULL, sizeof(*ps_lock), gfp);
ps_lock = klp_shadow_alloc(sta, PS_LOCK, sizeof(*ps_lock), gfp,
NULL, NULL);
if (!ps_lock)
goto shadow_fail;
spin_lock_init(ps_lock);
@ -131,7 +140,7 @@ variable:
void sta_info_free(struct ieee80211_local *local, struct sta_info *sta)
{
klp_shadow_free(sta, PS_LOCK);
klp_shadow_free(sta, PS_LOCK, NULL);
kfree(sta);
...
@ -148,16 +157,24 @@ shadow variables to parents already in-flight.
For commit 1d147bfa6429, a good spot to allocate a shadow spinlock is
inside ieee80211_sta_ps_deliver_wakeup():
int ps_lock_shadow_ctor(void *obj, void *shadow_data, void *ctor_data)
{
spinlock_t *lock = shadow_data;
spin_lock_init(lock);
return 0;
}
#define PS_LOCK 1
void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta)
{
DEFINE_SPINLOCK(ps_lock_fallback);
spinlock_t *ps_lock;
/* sync with ieee80211_tx_h_unicast_ps_buf */
ps_lock = klp_shadow_get_or_alloc(sta, PS_LOCK,
&ps_lock_fallback, sizeof(ps_lock_fallback),
GFP_ATOMIC);
sizeof(*ps_lock), GFP_ATOMIC,
ps_lock_shadow_ctor, NULL);
if (ps_lock)
spin_lock(ps_lock);
...

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@ -186,13 +186,20 @@ static inline bool klp_have_reliable_stack(void)
IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
}
typedef int (*klp_shadow_ctor_t)(void *obj,
void *shadow_data,
void *ctor_data);
typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
void *klp_shadow_get(void *obj, unsigned long id);
void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
size_t size, gfp_t gfp_flags);
void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
size_t size, gfp_t gfp_flags);
void klp_shadow_free(void *obj, unsigned long id);
void klp_shadow_free_all(unsigned long id);
void *klp_shadow_alloc(void *obj, unsigned long id,
size_t size, gfp_t gfp_flags,
klp_shadow_ctor_t ctor, void *ctor_data);
void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
size_t size, gfp_t gfp_flags,
klp_shadow_ctor_t ctor, void *ctor_data);
void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
#else /* !CONFIG_LIVEPATCH */

View File

@ -113,8 +113,10 @@ void *klp_shadow_get(void *obj, unsigned long id)
}
EXPORT_SYMBOL_GPL(klp_shadow_get);
static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
size_t size, gfp_t gfp_flags, bool warn_on_exist)
static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id,
size_t size, gfp_t gfp_flags,
klp_shadow_ctor_t ctor, void *ctor_data,
bool warn_on_exist)
{
struct klp_shadow *new_shadow;
void *shadow_data;
@ -125,18 +127,15 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
if (shadow_data)
goto exists;
/* Allocate a new shadow variable for use inside the lock below */
/*
* Allocate a new shadow variable. Fill it with zeroes by default.
* More complex setting can be done by @ctor function. But it is
* called only when the buffer is really used (under klp_shadow_lock).
*/
new_shadow = kzalloc(size + sizeof(*new_shadow), gfp_flags);
if (!new_shadow)
return NULL;
new_shadow->obj = obj;
new_shadow->id = id;
/* Initialize the shadow variable if data provided */
if (data)
memcpy(new_shadow->data, data, size);
/* Look for <obj, id> again under the lock */
spin_lock_irqsave(&klp_shadow_lock, flags);
shadow_data = klp_shadow_get(obj, id);
@ -150,6 +149,22 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
goto exists;
}
new_shadow->obj = obj;
new_shadow->id = id;
if (ctor) {
int err;
err = ctor(obj, new_shadow->data, ctor_data);
if (err) {
spin_unlock_irqrestore(&klp_shadow_lock, flags);
kfree(new_shadow);
pr_err("Failed to construct shadow variable <%p, %lx> (%d)\n",
obj, id, err);
return NULL;
}
}
/* No <obj, id> found, so attach the newly allocated one */
hash_add_rcu(klp_shadow_hash, &new_shadow->node,
(unsigned long)new_shadow->obj);
@ -170,26 +185,32 @@ exists:
* klp_shadow_alloc() - allocate and add a new shadow variable
* @obj: pointer to parent object
* @id: data identifier
* @data: pointer to data to attach to parent
* @size: size of attached data
* @gfp_flags: GFP mask for allocation
* @ctor: custom constructor to initialize the shadow data (optional)
* @ctor_data: pointer to any data needed by @ctor (optional)
*
* Allocates @size bytes for new shadow variable data using @gfp_flags
* and copies @size bytes from @data into the new shadow variable's own
* data space. If @data is NULL, @size bytes are still allocated, but
* no copy is performed. The new shadow variable is then added to the
* global hashtable.
* Allocates @size bytes for new shadow variable data using @gfp_flags.
* The data are zeroed by default. They are further initialized by @ctor
* function if it is not NULL. The new shadow variable is then added
* to the global hashtable.
*
* If an existing <obj, id> shadow variable can be found, this routine
* will issue a WARN, exit early and return NULL.
* If an existing <obj, id> shadow variable can be found, this routine will
* issue a WARN, exit early and return NULL.
*
* This function guarantees that the constructor function is called only when
* the variable did not exist before. The cost is that @ctor is called
* in atomic context under a spin lock.
*
* Return: the shadow variable data element, NULL on duplicate or
* failure.
*/
void *klp_shadow_alloc(void *obj, unsigned long id, void *data,
size_t size, gfp_t gfp_flags)
void *klp_shadow_alloc(void *obj, unsigned long id,
size_t size, gfp_t gfp_flags,
klp_shadow_ctor_t ctor, void *ctor_data)
{
return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, true);
return __klp_shadow_get_or_alloc(obj, id, size, gfp_flags,
ctor, ctor_data, true);
}
EXPORT_SYMBOL_GPL(klp_shadow_alloc);
@ -197,37 +218,51 @@ EXPORT_SYMBOL_GPL(klp_shadow_alloc);
* klp_shadow_get_or_alloc() - get existing or allocate a new shadow variable
* @obj: pointer to parent object
* @id: data identifier
* @data: pointer to data to attach to parent
* @size: size of attached data
* @gfp_flags: GFP mask for allocation
* @ctor: custom constructor to initialize the shadow data (optional)
* @ctor_data: pointer to any data needed by @ctor (optional)
*
* Returns a pointer to existing shadow data if an <obj, id> shadow
* variable is already present. Otherwise, it creates a new shadow
* variable like klp_shadow_alloc().
*
* This function guarantees that only one shadow variable exists with
* the given @id for the given @obj. It also guarantees that the shadow
* variable will be initialized by the given @data only when it did not
* exist before.
* This function guarantees that only one shadow variable exists with the given
* @id for the given @obj. It also guarantees that the constructor function
* will be called only when the variable did not exist before. The cost is
* that @ctor is called in atomic context under a spin lock.
*
* Return: the shadow variable data element, NULL on failure.
*/
void *klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data,
size_t size, gfp_t gfp_flags)
void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
size_t size, gfp_t gfp_flags,
klp_shadow_ctor_t ctor, void *ctor_data)
{
return __klp_shadow_get_or_alloc(obj, id, data, size, gfp_flags, false);
return __klp_shadow_get_or_alloc(obj, id, size, gfp_flags,
ctor, ctor_data, false);
}
EXPORT_SYMBOL_GPL(klp_shadow_get_or_alloc);
static void klp_shadow_free_struct(struct klp_shadow *shadow,
klp_shadow_dtor_t dtor)
{
hash_del_rcu(&shadow->node);
if (dtor)
dtor(shadow->obj, shadow->data);
kfree_rcu(shadow, rcu_head);
}
/**
* klp_shadow_free() - detach and free a <obj, id> shadow variable
* @obj: pointer to parent object
* @id: data identifier
* @dtor: custom callback that can be used to unregister the variable
* and/or free data that the shadow variable points to (optional)
*
* This function releases the memory for this <obj, id> shadow variable
* instance, callers should stop referencing it accordingly.
*/
void klp_shadow_free(void *obj, unsigned long id)
void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor)
{
struct klp_shadow *shadow;
unsigned long flags;
@ -239,8 +274,7 @@ void klp_shadow_free(void *obj, unsigned long id)
(unsigned long)obj) {
if (klp_shadow_match(shadow, obj, id)) {
hash_del_rcu(&shadow->node);
kfree_rcu(shadow, rcu_head);
klp_shadow_free_struct(shadow, dtor);
break;
}
}
@ -252,11 +286,13 @@ EXPORT_SYMBOL_GPL(klp_shadow_free);
/**
* klp_shadow_free_all() - detach and free all <*, id> shadow variables
* @id: data identifier
* @dtor: custom callback that can be used to unregister the variable
* and/or free data that the shadow variable points to (optional)
*
* This function releases the memory for all <*, id> shadow variable
* instances, callers should stop referencing them accordingly.
*/
void klp_shadow_free_all(unsigned long id)
void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor)
{
struct klp_shadow *shadow;
unsigned long flags;
@ -266,10 +302,8 @@ void klp_shadow_free_all(unsigned long id)
/* Delete all <*, id> from hash */
hash_for_each(klp_shadow_hash, i, shadow, node) {
if (klp_shadow_match(shadow, shadow->obj, id)) {
hash_del_rcu(&shadow->node);
kfree_rcu(shadow, rcu_head);
}
if (klp_shadow_match(shadow, shadow->obj, id))
klp_shadow_free_struct(shadow, dtor);
}
spin_unlock_irqrestore(&klp_shadow_lock, flags);

View File

@ -56,6 +56,21 @@ struct dummy {
unsigned long jiffies_expire;
};
/*
* The constructor makes more sense together with klp_shadow_get_or_alloc().
* In this example, it would be safe to assign the pointer also to the shadow
* variable returned by klp_shadow_alloc(). But we wanted to show the more
* complicated use of the API.
*/
static int shadow_leak_ctor(void *obj, void *shadow_data, void *ctor_data)
{
void **shadow_leak = shadow_data;
void *leak = ctor_data;
*shadow_leak = leak;
return 0;
}
struct dummy *livepatch_fix1_dummy_alloc(void)
{
struct dummy *d;
@ -74,7 +89,8 @@ struct dummy *livepatch_fix1_dummy_alloc(void)
* pointer to handle resource release.
*/
leak = kzalloc(sizeof(int), GFP_KERNEL);
klp_shadow_alloc(d, SV_LEAK, &leak, sizeof(leak), GFP_KERNEL);
klp_shadow_alloc(d, SV_LEAK, sizeof(leak), GFP_KERNEL,
shadow_leak_ctor, leak);
pr_info("%s: dummy @ %p, expires @ %lx\n",
__func__, d, d->jiffies_expire);
@ -82,9 +98,19 @@ struct dummy *livepatch_fix1_dummy_alloc(void)
return d;
}
static void livepatch_fix1_dummy_leak_dtor(void *obj, void *shadow_data)
{
void *d = obj;
void **shadow_leak = shadow_data;
kfree(*shadow_leak);
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
__func__, d, *shadow_leak);
}
void livepatch_fix1_dummy_free(struct dummy *d)
{
void **shadow_leak, *leak;
void **shadow_leak;
/*
* Patch: fetch the saved SV_LEAK shadow variable, detach and
@ -93,15 +119,10 @@ void livepatch_fix1_dummy_free(struct dummy *d)
* was loaded.)
*/
shadow_leak = klp_shadow_get(d, SV_LEAK);
if (shadow_leak) {
leak = *shadow_leak;
klp_shadow_free(d, SV_LEAK);
kfree(leak);
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
__func__, d, leak);
} else {
if (shadow_leak)
klp_shadow_free(d, SV_LEAK, livepatch_fix1_dummy_leak_dtor);
else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
}
kfree(d);
}
@ -147,7 +168,7 @@ static int livepatch_shadow_fix1_init(void)
static void livepatch_shadow_fix1_exit(void)
{
/* Cleanup any existing SV_LEAK shadow variables */
klp_shadow_free_all(SV_LEAK);
klp_shadow_free_all(SV_LEAK, livepatch_fix1_dummy_leak_dtor);
WARN_ON(klp_unregister_patch(&patch));
}

View File

@ -53,39 +53,42 @@ struct dummy {
bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
{
int *shadow_count;
int count;
/*
* Patch: handle in-flight dummy structures, if they do not
* already have a SV_COUNTER shadow variable, then attach a
* new one.
*/
count = 0;
shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
&count, sizeof(count),
GFP_NOWAIT);
sizeof(*shadow_count), GFP_NOWAIT,
NULL, NULL);
if (shadow_count)
*shadow_count += 1;
return time_after(jiffies, d->jiffies_expire);
}
static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
{
void *d = obj;
void **shadow_leak = shadow_data;
kfree(*shadow_leak);
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
__func__, d, *shadow_leak);
}
void livepatch_fix2_dummy_free(struct dummy *d)
{
void **shadow_leak, *leak;
void **shadow_leak;
int *shadow_count;
/* Patch: copy the memory leak patch from the fix1 module. */
shadow_leak = klp_shadow_get(d, SV_LEAK);
if (shadow_leak) {
leak = *shadow_leak;
klp_shadow_free(d, SV_LEAK);
kfree(leak);
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
__func__, d, leak);
} else {
if (shadow_leak)
klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
else
pr_info("%s: dummy @ %p leaked!\n", __func__, d);
}
/*
* Patch: fetch the SV_COUNTER shadow variable and display
@ -95,7 +98,7 @@ void livepatch_fix2_dummy_free(struct dummy *d)
if (shadow_count) {
pr_info("%s: dummy @ %p, check counter = %d\n",
__func__, d, *shadow_count);
klp_shadow_free(d, SV_COUNTER);
klp_shadow_free(d, SV_COUNTER, NULL);
}
kfree(d);
@ -142,7 +145,7 @@ static int livepatch_shadow_fix2_init(void)
static void livepatch_shadow_fix2_exit(void)
{
/* Cleanup any existing SV_COUNTER shadow variables */
klp_shadow_free_all(SV_COUNTER);
klp_shadow_free_all(SV_COUNTER, NULL);
WARN_ON(klp_unregister_patch(&patch));
}