[Linux-kernel-mentees] [PATCH] net: team: fix memory leak in __team_options_register

[Linux-kernel-mentees] [PATCH] net: team: fix memory leak in __team_options_register

[Anant Thazhemadam]

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@syzkaller.appspotmail.com
Tested-by: syzbot+69b804437cfec30deac3@syzkaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.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

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Re: [Linux-kernel-mentees] [PATCH] net: team: fix memory leak in __team_options_register

[David Miller]

From: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Date: Mon,  5 Oct 2020 02:25:36 +0530

> 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@syzkaller.appspotmail.com
> Tested-by: syzbot+69b804437cfec30deac3@syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>

Applied and queued up for -stable, thank you.
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