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Commit 41e3bef5 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 36e584de 3b2c77d0

Documentation/livepatch/shadow-vars.txt

+29 −12
Original line number Diff line number Diff line
@@ -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);

	...

include/linux/livepatch.h

+13 −6
Original line number Diff line number Diff line
@@ -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 */

kernel/livepatch/shadow.c

+71 −37
Original line number Diff line number Diff line
@@ -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 @@ static void *__klp_shadow_get_or_alloc(void *obj, unsigned long id, void *data, 
 * 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);

samples/livepatch/livepatch-shadow-fix1.c

+32 −11
Original line number Diff line number Diff line
@@ -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));

}

samples/livepatch/livepatch-shadow-fix2.c

+18 −15
Original line number Diff line number Diff line
@@ -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));

}