From cdf5976fcb7328875a0216a94ae7dafd4ee3abfb Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 20 Oct 2017 10:57:57 +0300 Subject: sparc64: convert mdesc_handle.refcnt from atomic_t to refcount_t atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable mdesc_handle.refcnt is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Acked-by: Shannon Nelson Signed-off-by: David S. Miller --- arch/sparc/kernel/mdesc.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'arch/sparc') diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c index fa466ce45bc9..821a7247a037 100644 --- a/arch/sparc/kernel/mdesc.c +++ b/arch/sparc/kernel/mdesc.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include @@ -70,7 +71,7 @@ struct mdesc_handle { struct list_head list; struct mdesc_mem_ops *mops; void *self_base; - atomic_t refcnt; + refcount_t refcnt; unsigned int handle_size; struct mdesc_hdr mdesc; }; @@ -152,7 +153,7 @@ static void mdesc_handle_init(struct mdesc_handle *hp, memset(hp, 0, handle_size); INIT_LIST_HEAD(&hp->list); hp->self_base = base; - atomic_set(&hp->refcnt, 1); + refcount_set(&hp->refcnt, 1); hp->handle_size = handle_size; } @@ -182,7 +183,7 @@ static void __init mdesc_memblock_free(struct mdesc_handle *hp) unsigned int alloc_size; unsigned long start; - BUG_ON(atomic_read(&hp->refcnt) != 0); + BUG_ON(refcount_read(&hp->refcnt) != 0); BUG_ON(!list_empty(&hp->list)); alloc_size = PAGE_ALIGN(hp->handle_size); @@ -220,7 +221,7 @@ static struct mdesc_handle *mdesc_kmalloc(unsigned int mdesc_size) static void mdesc_kfree(struct mdesc_handle *hp) { - BUG_ON(atomic_read(&hp->refcnt) != 0); + BUG_ON(refcount_read(&hp->refcnt) != 0); BUG_ON(!list_empty(&hp->list)); kfree(hp->self_base); @@ -259,7 +260,7 @@ struct mdesc_handle *mdesc_grab(void) spin_lock_irqsave(&mdesc_lock, flags); hp = cur_mdesc; if (hp) - atomic_inc(&hp->refcnt); + refcount_inc(&hp->refcnt); spin_unlock_irqrestore(&mdesc_lock, flags); return hp; @@ -271,7 +272,7 @@ void mdesc_release(struct mdesc_handle *hp) unsigned long flags; spin_lock_irqsave(&mdesc_lock, flags); - if (atomic_dec_and_test(&hp->refcnt)) { + if (refcount_dec_and_test(&hp->refcnt)) { list_del_init(&hp->list); hp->mops->free(hp); } @@ -513,7 +514,7 @@ void mdesc_update(void) if (status != HV_EOK || real_len > len) { printk(KERN_ERR "MD: mdesc reread fails with %lu\n", status); - atomic_dec(&hp->refcnt); + refcount_dec(&hp->refcnt); mdesc_free(hp); goto out; } @@ -526,7 +527,7 @@ void mdesc_update(void) mdesc_notify_clients(orig_hp, hp); spin_lock_irqsave(&mdesc_lock, flags); - if (atomic_dec_and_test(&orig_hp->refcnt)) + if (refcount_dec_and_test(&orig_hp->refcnt)) mdesc_free(orig_hp); else list_add(&orig_hp->list, &mdesc_zombie_list); -- cgit