[PATCH] ftrace: Check if pages were allocated before calling free_pages()

[Jiapeng Chong]

It is possible that on error pg->size can be zero when getting its
order,which would return a -1 value. It is dangerous to pass in an
order of -1 to free_pages(). Check if order is greater than or equal
to zero before calling free_pages().

Reported-by: Abaci Robot <ab...@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.ch...@linux.alibaba.com>
---
 kernel/trace/ftrace.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b7e29db..74efc33 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6811,7 +6811,8 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, 
void *end_ptr)
                if (!pg->index) {
                        *last_pg = pg->next;
                        order = get_count_order(pg->size / ENTRIES_PER_PAGE);
-                       free_pages((unsigned long)pg->records, order);
+                       if (order >= 0)
+                               free_pages((unsigned long)pg->records, order);
                        ftrace_number_of_pages -= 1 << order;
                        ftrace_number_of_groups--;
                        kfree(pg);
-- 
1.8.3.1