linux-kernel - [PATCH] ftrace: Check if pages were allocated before calling free

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Date:   Tue,  6 Apr 2021 14:51:45 +0800
From:   Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
To:     rostedt@...dmis.org
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Subject: [PATCH] ftrace: Check if pages were allocated before calling free_pages()

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@...ux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.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