linux-kernel - [PATCH] team: Fix use-after-free when an option instance allocation fails

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Message-ID: <20231206123719.1963153-1-revest@chromium.org>
Date:   Wed,  6 Dec 2023 13:37:18 +0100
From:   Florent Revest <revest@...omium.org>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com,
        Florent Revest <revest@...omium.org>
Subject: [PATCH] team: Fix use-after-free when an option instance allocation fails

In __team_options_register, team_options are allocated and appended to
the team's option_list.
If one option instance allocation fails, the "inst_rollback" cleanup
path frees the previously allocated options but doesn't remove them from
the team's option_list.
This leaves dangling pointers that can be dereferenced later by other
parts of the team driver that iterate over options.

This patch fixes the cleanup path to remove the dangling pointers from
the list.

As far as I can tell, this uaf doesn't have much security implications
since it would be fairly hard to exploit (an attacker would need to make
the allocation of that specific small object fail) but it's still nice
to fix.

Fixes: 80f7c6683fe0 ("team: add support for per-port options")
Signed-off-by: Florent Revest <revest@...omium.org>
---
 drivers/net/team/team.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
index 508d9a392ab18..f575f225d4178 100644
--- a/drivers/net/team/team.c
+++ b/drivers/net/team/team.c
@@ -281,8 +281,10 @@ static int __team_options_register(struct team *team,
 	return 0;

 inst_rollback:
-	for (i--; i >= 0; i--)
+	for (i--; i >= 0; i--) {
 		__team_option_inst_del_option(team, dst_opts[i]);
+		list_del(&dst_opts[i]->list);
+	}

 	i = option_count;
 alloc_rollback:
-- 
2.43.0.rc2.451.g8631bc7472-goog