linux-kernel - [PATCH] net: team: fix memory leak in __team_options

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Message-Id: <20201004205536.4734-1-anant.thazhemadam@gmail.com>
Date:   Mon,  5 Oct 2020 02:25:36 +0530
From:   Anant Thazhemadam <anant.thazhemadam@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        Anant Thazhemadam <anant.thazhemadam@...il.com>,
        syzbot+69b804437cfec30deac3@...kaller.appspotmail.com,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] net: team: fix memory leak in __team_options_register

The variable "i" isn't initialized back correctly after the first loop
under the label inst_rollback gets executed.

The value of "i" is assigned to be option_count - 1, and the ensuing 
loop (under alloc_rollback) begins by initializing i--. 
Thus, the value of i when the loop begins execution will now become 
i = option_count - 2.

Thus, when kfree(dst_opts[i]) is called in the second loop in this 
order, (i.e., inst_rollback followed by alloc_rollback), 
dst_optsp[option_count - 2] is the first element freed, and 
dst_opts[option_count - 1] does not get freed, and thus, a memory 
leak is caused.

This memory leak can be fixed, by assigning i = option_count (instead of
option_count - 1).

Fixes: 80f7c6683fe0 ("team: add support for per-port options")
Reported-by: syzbot+69b804437cfec30deac3@...kaller.appspotmail.com
Tested-by: syzbot+69b804437cfec30deac3@...kaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@...il.com>
---
 drivers/net/team/team.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
index 8c1e02752ff6..8986f3ffffe4 100644
--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -287,7 +287,7 @@ static int __team_options_register(struct team *team,
 	for (i--; i >= 0; i--)
 		__team_option_inst_del_option(team, dst_opts[i]);

-	i = option_count - 1;
+	i = option_count;
 alloc_rollback:
 	for (i--; i >= 0; i--)
 		kfree(dst_opts[i]);
-- 
2.25.1