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Commit 06a51d93 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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ftrace: Create ftrace_hash_empty() helper routine 



There are two types of hashes in the ftrace_ops; one type
is the filter_hash and the other is the notrace_hash. Either
one may be null, meaning it has no elements. But when elements
are added, the hash is allocated.

Throughout the code, a check needs to be made to see if a hash
exists or the hash has elements, but the check if the hash exists
is usually missing causing the possible "NULL pointer dereference bug".

Add a helper routine called "ftrace_hash_empty()" that returns
true if the hash doesn't exist or its count is zero. As they mean
the same thing.

Last-bug-reported-by: default avatarJiri Olsa <jolsa@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent c842e975

kernel/trace/ftrace.c

+17 −11
Original line number Diff line number Diff line
@@ -999,6 +999,11 @@ static struct ftrace_page *ftrace_new_pgs; 
static struct ftrace_page	*ftrace_pages_start;

static struct ftrace_page	*ftrace_pages;



static bool ftrace_hash_empty(struct ftrace_hash *hash)

{

	return !hash || !hash->count;

}



static struct ftrace_func_entry *

ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip)

{
@@ -1007,7 +1012,7 @@ ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip) 
	struct hlist_head *hhd;

	struct hlist_node *n;



	if (!hash->count)

	if (ftrace_hash_empty(hash))

		return NULL;



	if (hash->size_bits > 0)
@@ -1151,7 +1156,7 @@ alloc_and_copy_ftrace_hash(int size_bits, struct ftrace_hash *hash) 
		return NULL;



	/* Empty hash? */

	if (!hash || !hash->count)

	if (ftrace_hash_empty(hash))

		return new_hash;



	size = 1 << hash->size_bits;
@@ -1276,9 +1281,9 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip) 
	filter_hash = rcu_dereference_raw(ops->filter_hash);

	notrace_hash = rcu_dereference_raw(ops->notrace_hash);



	if ((!filter_hash || !filter_hash->count ||

	if ((ftrace_hash_empty(filter_hash) ||

	     ftrace_lookup_ip(filter_hash, ip)) &&

	    (!notrace_hash || !notrace_hash->count ||

	    (ftrace_hash_empty(notrace_hash) ||

	     !ftrace_lookup_ip(notrace_hash, ip)))

		ret = 1;

	else
@@ -1371,7 +1376,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops, 
	if (filter_hash) {

		hash = ops->filter_hash;

		other_hash = ops->notrace_hash;

		if (!hash || !hash->count)

		if (ftrace_hash_empty(hash))

			all = 1;

	} else {

		inc = !inc;
@@ -1381,7 +1386,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops, 
		 * If the notrace hash has no items,

		 * then there's nothing to do.

		 */

		if (!hash || !hash->count)

		if (ftrace_hash_empty(hash))

			return;

	}
@@ -1398,8 +1403,8 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops, 
			if (!other_hash || !ftrace_lookup_ip(other_hash, rec->ip))

				match = 1;

		} else {

			in_hash = hash && !!ftrace_lookup_ip(hash, rec->ip);

			in_other_hash = other_hash && !!ftrace_lookup_ip(other_hash, rec->ip);

			in_hash = !!ftrace_lookup_ip(hash, rec->ip);

			in_other_hash = !!ftrace_lookup_ip(other_hash, rec->ip);



			/*

			 *
@@ -1407,7 +1412,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops, 
			if (filter_hash && in_hash && !in_other_hash)

				match = 1;

			else if (!filter_hash && in_hash &&

				 (in_other_hash || !other_hash->count))

				 (in_other_hash || ftrace_hash_empty(other_hash)))

				match = 1;

		}

		if (!match)
@@ -1950,7 +1955,7 @@ static int ops_traces_mod(struct ftrace_ops *ops) 
	struct ftrace_hash *hash;



	hash = ops->filter_hash;

	return !!(!hash || !hash->count);

	return ftrace_hash_empty(hash);

}



static int ftrace_update_code(struct module *mod)
@@ -2320,7 +2325,8 @@ static void *t_start(struct seq_file *m, loff_t *pos) 
	 * off, we can short cut and just print out that all

	 * functions are enabled.

	 */

	if (iter->flags & FTRACE_ITER_FILTER && !ops->filter_hash->count) {

	if (iter->flags & FTRACE_ITER_FILTER &&

	    ftrace_hash_empty(ops->filter_hash)) {

		if (*pos > 0)

			return t_hash_start(m, pos);

		iter->flags |= FTRACE_ITER_PRINTALL;