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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: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2011-12-19 19:07:36 -05:00 committed by Steven Rostedt
parent c842e97552
commit 06a51d9307
1 changed files with 17 additions and 11 deletions
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28
kernel/trace/ftrace.c
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@ -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;