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authorLinus Torvalds <torvalds@linux-foundation.org>2018-04-20 08:51:55 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-20 08:51:55 -0700
commit41e3bef52e42c03cb7234f2d8419352478c92926 (patch)
treefb704ba35a9263084a4606d1d326c90cd1591c40 /kernel
parent36e584de256a8155a292a96288bd78a3a328aa4f (diff)
parent3b2c77d000fe9f7d02e9e726e00dccf9f92b256f (diff)
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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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/livepatch/shadow.c108
1 files changed, 71 insertions, 37 deletions
diff --git a/kernel/livepatch/shadow.c b/kernel/livepatch/shadow.c
index fdac27588d60..83958c814439 100644
--- a/kernel/livepatch/shadow.c
+++ b/kernel/livepatch/shadow.c
@@ -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.
+ * 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.
*
- * 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.
+ * 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);