From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D77C38E8BE; Tue, 7 Jul 2026 10:18:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783419494; cv=none; b=WfxcYQdAYHu903oOZsmByqauga+IdJYjs9MB31MIbSkAQrRzc7NE+m9JERqzkiPe9uAJdT3BTZXFiKlLUvQhjPs3sBL4oByjK6iPv/ku/lZAXbaMHgzQAyQTU9U9SfKb2ze0tysntpwg3aDjLOvp5FrqD6BLYzKOKVKZAoxMZGU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783419494; c=relaxed/simple; bh=u+Dd3Ym2PdPJsp/ejcuh3zKgHUyuIvnmV3NHhz1X0K8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=n2ATtF/h4Xt9KVsnuWPVeUqmTfBnnqfqvckuoMK0TqfvAESLH1WmcjvxE10S566VTbqjEVBII9SpDEFxqAo3YlbIqNm3Q/DacUd+Kf4vJfQyJXW1dPOOjF2gzEu4UKzO2polgyPtXhd9nrLdEULFYr0M2+Y3CZnCMdSMhxW40zg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Hnw8hPmg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Hnw8hPmg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE9DC1F000E9; Tue, 7 Jul 2026 10:18:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783419492; bh=ylYhXURXRgJBX9/4ChaluiVfa0Om9yKIIy1I0NWmAqM=; h=From:To:Cc:Subject:Date; b=Hnw8hPmgv/hHI3TlHCjogcV98alJ00ZRuYrFiBmkr2/IbF34VdOybGUy1WKKnxK+X zRUkbQiVtuZvJJ1qb46QmZVDnLmTLTmLE/ZU7CA8scXNoMzH4RhbgqiY4wiD8BZyGX xTWMrBpExsQMd70yH9Ou32dkTajeStSEg10ig//w4Coml/L1mB+wsb++CMDNKCKkZl WmUjgtcxEJDs1XMdbNEDv3NzzVzJ09oFcHky8qVFAAqgagSQTufkKbv4xjVwe41gl7 n4R6n3KSZ9wtFkyZyfyL4pi66s4UhglrIjElLC1j92xzzFo7iAzGUMhHmWizoH4G8x 6prWkwim2tCkg== From: Tzung-Bi Shih To: Wim Van Sebroeck , Guenter Roeck Cc: linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org, tzungbi@kernel.org Subject: [PATCH] watchdog: pretimeout: Fix UAF in watchdog_unregister_governor() Date: Tue, 7 Jul 2026 10:18:03 +0000 Message-ID: <20260707101803.3598173-1-tzungbi@kernel.org> X-Mailer: git-send-email 2.55.0.rc2.803.g1fd1e6609c-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a watchdog governor is unregistered, it updates existing watchdog devices that were using this governor by falling back to `default_gov`. If the governor being unregistered is currently set as `default_gov`, the `default_gov` is never cleared. This leads to 2 use-after-free issues: 1. New watchdog devices registered after this point will inherit the dangling `default_gov`. 2. Existing watchdog devices using the unregistered governor will have their `wdd->gov` reassigned to the dangling `default_gov`. Fix the UAF by clearing `default_gov` if it matches the governor being unregistered. Fixes: da0d12ff2b82 ("watchdog: pretimeout: add panic pretimeout governor") Signed-off-by: Tzung-Bi Shih --- drivers/watchdog/watchdog_pretimeout.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/watchdog/watchdog_pretimeout.c b/drivers/watchdog/watchdog_pretimeout.c index 19eb2ed2c7cb..02e09b9e396d 100644 --- a/drivers/watchdog/watchdog_pretimeout.c +++ b/drivers/watchdog/watchdog_pretimeout.c @@ -167,6 +167,8 @@ void watchdog_unregister_governor(struct watchdog_governor *gov) } spin_lock_irq(&pretimeout_lock); + if (default_gov == gov) + default_gov = NULL; list_for_each_entry(p, &pretimeout_list, entry) if (p->wdd->gov == gov) p->wdd->gov = default_gov; -- 2.55.0.rc2.803.g1fd1e6609c-goog