Merge remote-tracking branch 'tip/auto-latest'

2 files changed, 145 insertions, 52 deletions

diff --git a/lib/bug.c b/lib/bug.c
index 06edbbef0623..a6a1137d06db 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -47,7 +47,7 @@
 #include <linux/sched.h>
 #include <linux/rculist.h>
 
-extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
+extern struct bug_entry __start___bug_table[], __stop___bug_table[];
 
 static inline unsigned long bug_addr(const struct bug_entry *bug)
 {
@@ -62,10 +62,10 @@ static inline unsigned long bug_addr(const struct bug_entry *bug)
 /* Updates are protected by module mutex */
 static LIST_HEAD(module_bug_list);
 
-static const struct bug_entry *module_find_bug(unsigned long bugaddr)
+static struct bug_entry *module_find_bug(unsigned long bugaddr)
 {
 	struct module *mod;
-	const struct bug_entry *bug = NULL;
+	struct bug_entry *bug = NULL;
 
 	rcu_read_lock_sched();
 	list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
@@ -122,15 +122,15 @@ void module_bug_cleanup(struct module *mod)
 
 #else
 
-static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
+static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
 {
 	return NULL;
 }
 #endif
 
-const struct bug_entry *find_bug(unsigned long bugaddr)
+struct bug_entry *find_bug(unsigned long bugaddr)
 {
-	const struct bug_entry *bug;
+	struct bug_entry *bug;
 
 	for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
 		if (bugaddr == bug_addr(bug))
@@ -141,9 +141,9 @@ const struct bug_entry *find_bug(unsigned long bugaddr)
 
 enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 {
-	const struct bug_entry *bug;
+	struct bug_entry *bug;
 	const char *file;
-	unsigned line, warning;
+	unsigned line, warning, once, done;
 
 	if (!is_valid_bugaddr(bugaddr))
 		return BUG_TRAP_TYPE_NONE;
@@ -164,6 +164,18 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 		line = bug->line;
 #endif
 		warning = (bug->flags & BUGFLAG_WARNING) != 0;
+		once = (bug->flags & BUGFLAG_ONCE) != 0;
+		done = (bug->flags & BUGFLAG_DONE) != 0;
+
+		if (warning && once) {
+			if (done)
+				return BUG_TRAP_TYPE_WARN;
+
+			/*
+			 * Since this is the only store, concurrency is not an issue.
+			 */
+			bug->flags |= BUGFLAG_DONE;
+		}
 	}
 
 	if (warning) {
diff --git a/lib/refcount.c b/lib/refcount.c
index aa09ad3c30b0..f42124ccf295 100644
--- a/lib/refcount.c
+++ b/lib/refcount.c
@@ -37,11 +37,29 @@
 #include <linux/refcount.h>
 #include <linux/bug.h>
 
+/**
+ * refcount_add_not_zero - add a value to a refcount unless it is 0
+ * @i: the value to add to the refcount
+ * @r: the refcount
+ *
+ * Will saturate at UINT_MAX and WARN.
+ *
+ * Provides no memory ordering, it is assumed the caller has guaranteed the
+ * object memory to be stable (RCU, etc.). It does provide a control dependency
+ * and thereby orders future stores. See the comment on top.
+ *
+ * Use of this function is not recommended for the normal reference counting
+ * use case in which references are taken and released one at a time.  In these
+ * cases, refcount_inc(), or one of its variants, should instead be used to
+ * increment a reference count.
+ *
+ * Return: false if the passed refcount is 0, true otherwise
+ */
 bool refcount_add_not_zero(unsigned int i, refcount_t *r)
 {
-	unsigned int old, new, val = atomic_read(&r->refs);
+	unsigned int new, val = atomic_read(&r->refs);
 
-	for (;;) {
+	do {
 		if (!val)
 			return false;
 
@@ -51,12 +69,8 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r)
 		new = val + i;
 		if (new < val)
 			new = UINT_MAX;
-		old = atomic_cmpxchg_relaxed(&r->refs, val, new);
-		if (old == val)
-			break;
 
-		val = old;
-	}
+	} while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
 
 	WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
 
@@ -64,24 +78,45 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r)
 }
 EXPORT_SYMBOL_GPL(refcount_add_not_zero);
 
+/**
+ * refcount_add - add a value to a refcount
+ * @i: the value to add to the refcount
+ * @r: the refcount
+ *
+ * Similar to atomic_add(), but will saturate at UINT_MAX and WARN.
+ *
+ * Provides no memory ordering, it is assumed the caller has guaranteed the
+ * object memory to be stable (RCU, etc.). It does provide a control dependency
+ * and thereby orders future stores. See the comment on top.
+ *
+ * Use of this function is not recommended for the normal reference counting
+ * use case in which references are taken and released one at a time.  In these
+ * cases, refcount_inc(), or one of its variants, should instead be used to
+ * increment a reference count.
+ */
 void refcount_add(unsigned int i, refcount_t *r)
 {
 	WARN_ONCE(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
 }
 EXPORT_SYMBOL_GPL(refcount_add);
 
-/*
- * Similar to atomic_inc_not_zero(), will saturate at UINT_MAX and WARN.
+/**
+ * refcount_inc_not_zero - increment a refcount unless it is 0
+ * @r: the refcount to increment
+ *
+ * Similar to atomic_inc_not_zero(), but will saturate at UINT_MAX and WARN.
  *
  * Provides no memory ordering, it is assumed the caller has guaranteed the
  * object memory to be stable (RCU, etc.). It does provide a control dependency
  * and thereby orders future stores. See the comment on top.
+ *
+ * Return: true if the increment was successful, false otherwise
  */
 bool refcount_inc_not_zero(refcount_t *r)
 {
-	unsigned int old, new, val = atomic_read(&r->refs);
+	unsigned int new, val = atomic_read(&r->refs);
 
-	for (;;) {
+	do {
 		new = val + 1;
 
 		if (!val)
@@ -90,12 +125,7 @@ bool refcount_inc_not_zero(refcount_t *r)
 		if (unlikely(!new))
 			return true;
 
-		old = atomic_cmpxchg_relaxed(&r->refs, val, new);
-		if (old == val)
-			break;
-
-		val = old;
-	}
+	} while (!atomic_try_cmpxchg_relaxed(&r->refs, &val, new));
 
 	WARN_ONCE(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
 
@@ -103,11 +133,17 @@ bool refcount_inc_not_zero(refcount_t *r)
 }
 EXPORT_SYMBOL_GPL(refcount_inc_not_zero);
 
-/*
- * Similar to atomic_inc(), will saturate at UINT_MAX and WARN.
+/**
+ * refcount_inc - increment a refcount
+ * @r: the refcount to increment
+ *
+ * Similar to atomic_inc(), but will saturate at UINT_MAX and WARN.
  *
  * Provides no memory ordering, it is assumed the caller already has a
- * reference on the object, will WARN when this is not so.
+ * reference on the object.
+ *
+ * Will WARN if the refcount is 0, as this represents a possible use-after-free
+ * condition.
  */
 void refcount_inc(refcount_t *r)
 {
@@ -115,11 +151,31 @@ void refcount_inc(refcount_t *r)
 }
 EXPORT_SYMBOL_GPL(refcount_inc);
 
+/**
+ * refcount_sub_and_test - subtract from a refcount and test if it is 0
+ * @i: amount to subtract from the refcount
+ * @r: the refcount
+ *
+ * Similar to atomic_dec_and_test(), but it will WARN, return false and
+ * ultimately leak on underflow and will fail to decrement when saturated
+ * at UINT_MAX.
+ *
+ * Provides release memory ordering, such that prior loads and stores are done
+ * before, and provides a control dependency such that free() must come after.
+ * See the comment on top.
+ *
+ * Use of this function is not recommended for the normal reference counting
+ * use case in which references are taken and released one at a time.  In these
+ * cases, refcount_dec(), or one of its variants, should instead be used to
+ * decrement a reference count.
+ *
+ * Return: true if the resulting refcount is 0, false otherwise
+ */
 bool refcount_sub_and_test(unsigned int i, refcount_t *r)
 {
-	unsigned int old, new, val = atomic_read(&r->refs);
+	unsigned int new, val = atomic_read(&r->refs);
 
-	for (;;) {
+	do {
 		if (unlikely(val == UINT_MAX))
 			return false;
 
@@ -129,24 +185,24 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r)
 			return false;
 		}
 
-		old = atomic_cmpxchg_release(&r->refs, val, new);
-		if (old == val)
-			break;
-
-		val = old;
-	}
+	} while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
 
 	return !new;
 }
 EXPORT_SYMBOL_GPL(refcount_sub_and_test);
 
-/*
+/**
+ * refcount_dec_and_test - decrement a refcount and test if it is 0
+ * @r: the refcount
+ *
  * Similar to atomic_dec_and_test(), it will WARN on underflow and fail to
  * decrement when saturated at UINT_MAX.
  *
  * Provides release memory ordering, such that prior loads and stores are done
  * before, and provides a control dependency such that free() must come after.
  * See the comment on top.
+ *
+ * Return: true if the resulting refcount is 0, false otherwise
  */
 bool refcount_dec_and_test(refcount_t *r)
 {
@@ -154,21 +210,26 @@ bool refcount_dec_and_test(refcount_t *r)
 }
 EXPORT_SYMBOL_GPL(refcount_dec_and_test);
 
-/*
+/**
+ * refcount_dec - decrement a refcount
+ * @r: the refcount
+ *
  * Similar to atomic_dec(), it will WARN on underflow and fail to decrement
  * when saturated at UINT_MAX.
  *
  * Provides release memory ordering, such that prior loads and stores are done
  * before.
  */
-
 void refcount_dec(refcount_t *r)
 {
 	WARN_ONCE(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
 }
 EXPORT_SYMBOL_GPL(refcount_dec);
 
-/*
+/**
+ * refcount_dec_if_one - decrement a refcount if it is 1
+ * @r: the refcount
+ *
  * No atomic_t counterpart, it attempts a 1 -> 0 transition and returns the
  * success thereof.
  *
@@ -178,24 +239,33 @@ EXPORT_SYMBOL_GPL(refcount_dec);
  * It can be used like a try-delete operator; this explicit case is provided
  * and not cmpxchg in generic, because that would allow implementing unsafe
  * operations.
+ *
+ * Return: true if the resulting refcount is 0, false otherwise
  */
 bool refcount_dec_if_one(refcount_t *r)
 {
-	return atomic_cmpxchg_release(&r->refs, 1, 0) == 1;
+	int val = 1;
+
+	return atomic_try_cmpxchg_release(&r->refs, &val, 0);
 }
 EXPORT_SYMBOL_GPL(refcount_dec_if_one);
 
-/*
+/**
+ * refcount_dec_not_one - decrement a refcount if it is not 1
+ * @r: the refcount
+ *
  * No atomic_t counterpart, it decrements unless the value is 1, in which case
  * it will return false.
  *
  * Was often done like: atomic_add_unless(&var, -1, 1)
+ *
+ * Return: true if the decrement operation was successful, false otherwise
  */
 bool refcount_dec_not_one(refcount_t *r)
 {
-	unsigned int old, new, val = atomic_read(&r->refs);
+	unsigned int new, val = atomic_read(&r->refs);
 
-	for (;;) {
+	do {
 		if (unlikely(val == UINT_MAX))
 			return true;
 
@@ -208,24 +278,27 @@ bool refcount_dec_not_one(refcount_t *r)
 			return true;
 		}
 
-		old = atomic_cmpxchg_release(&r->refs, val, new);
-		if (old == val)
-			break;
-
-		val = old;
-	}
+	} while (!atomic_try_cmpxchg_release(&r->refs, &val, new));
 
 	return true;
 }
 EXPORT_SYMBOL_GPL(refcount_dec_not_one);
 
-/*
+/**
+ * refcount_dec_and_mutex_lock - return holding mutex if able to decrement
+ *                               refcount to 0
+ * @r: the refcount
+ * @lock: the mutex to be locked
+ *
  * Similar to atomic_dec_and_mutex_lock(), it will WARN on underflow and fail
  * to decrement when saturated at UINT_MAX.
  *
  * Provides release memory ordering, such that prior loads and stores are done
  * before, and provides a control dependency such that free() must come after.
  * See the comment on top.
+ *
+ * Return: true and hold mutex if able to decrement refcount to 0, false
+ *         otherwise
  */
 bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
 {
@@ -242,13 +315,21 @@ bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock)
 }
 EXPORT_SYMBOL_GPL(refcount_dec_and_mutex_lock);
 
-/*
+/**
+ * refcount_dec_and_lock - return holding spinlock if able to decrement
+ *                         refcount to 0
+ * @r: the refcount
+ * @lock: the spinlock to be locked
+ *
  * Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
  * decrement when saturated at UINT_MAX.
  *
  * Provides release memory ordering, such that prior loads and stores are done
  * before, and provides a control dependency such that free() must come after.
  * See the comment on top.
+ *
+ * Return: true and hold spinlock if able to decrement refcount to 0, false
+ *         otherwise
  */
 bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock)
 {