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

[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 <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@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

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

[Steven Rostedt]

On Tue,  6 Apr 2021 14:51:45 +0800
Jiapeng Chong <jiapeng.chong@linux.alibaba.com> wrote:

> 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 <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@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);

This has already been fixed upstream.

-- Steve

>  			ftrace_number_of_pages -= 1 << order;
>  			ftrace_number_of_groups--;
>  			kfree(pg);