linux-kernel - [PATCH AUTOSEL 5.10 08/22] ftrace: Check if pages were allocated before calling free

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Message-Id: <20210405160432.268374-8-sashal@kernel.org>
Date:   Mon,  5 Apr 2021 12:04:17 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Abaci Robot <abaci@...ux.alibaba.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.10 08/22] ftrace: Check if pages were allocated before calling free_pages()

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

[ Upstream commit 59300b36f85f254260c81d9dd09195fa49eb0f98 ]

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().

Link: https://lore.kernel.org/lkml/20210330093916.432697c7@gandalf.local.home/

Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/trace/ftrace.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 82041bbf8fc2..b1983c2aeb53 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3230,7 +3230,8 @@ ftrace_allocate_pages(unsigned long num_to_init)
 	pg = start_pg;
 	while (pg) {
 		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);
 		start_pg = pg->next;
 		kfree(pg);
 		pg = start_pg;
@@ -6452,7 +6453,8 @@ void ftrace_release_mod(struct module *mod)
 		clear_mod_from_hashes(pg);
 
 		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);
 		tmp_page = pg->next;
 		kfree(pg);
 		ftrace_number_of_pages -= 1 << order;
@@ -6812,7 +6814,8 @@ 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);
-- 
2.30.2