linux-kernel - [PATCH v1] clk: microchip: fix potential UAF in auxdev release callback

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Message-Id: <20230413-critter-synopsis-dac070a86cb4@spud>
Date:   Thu, 13 Apr 2023 23:20:45 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     conor@...nel.org, Conor Dooley <conor.dooley@...rochip.com>,
        stable@...r.kernel.org,
        Daire McNamara <daire.mcnamara@...rochip.com>,
        Michael Turquette <mturquette@...libre.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] clk: microchip: fix potential UAF in auxdev release callback

From: Conor Dooley <conor.dooley@...rochip.com>

Similar to commit 1c11289b34ab ("peci: cpu: Fix use-after-free in
adev_release()"), the auxiliary device is not torn down in the correct
order. If auxiliary_device_add() fails, the release callback will be
called twice, resulting in a UAF. Due to timing, the auxdev code in this
driver "took inspiration" from the aforementioned commit, and thus its
bugs too!

Moving auxiliary_device_uninit() to the unregister callback instead
avoids the issue.

CC: stable@...r.kernel.org
Fixes: b56bae2dd6fd ("clk: microchip: mpfs: add reset controller")
Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
---
Stephen,
Claudiu is on leave at the moment, and although I can push stuff to the
at-91 tree etc, it's probably simpler if you just take this yourself?

CC: Stephen Boyd <sboyd@...nel.org>
CC: Conor Dooley <conor.dooley@...rochip.com>
CC: Daire McNamara <daire.mcnamara@...rochip.com>
CC: Michael Turquette <mturquette@...libre.com>
CC: Stephen Boyd <sboyd@...nel.org>
CC: Claudiu Beznea <claudiu.beznea@...rochip.com>
CC: linux-clk@...r.kernel.org
CC: linux-kernel@...r.kernel.org
---
 drivers/clk/microchip/clk-mpfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/clk/microchip/clk-mpfs.c b/drivers/clk/microchip/clk-mpfs.c
index 4f0a19db7ed7..cc5d7dee59f0 100644
--- a/drivers/clk/microchip/clk-mpfs.c
+++ b/drivers/clk/microchip/clk-mpfs.c
@@ -374,14 +374,13 @@ static void mpfs_reset_unregister_adev(void *_adev)
 	struct auxiliary_device *adev = _adev;
 
 	auxiliary_device_delete(adev);
+	auxiliary_device_uninit(adev);
 }
 
 static void mpfs_reset_adev_release(struct device *dev)
 {
 	struct auxiliary_device *adev = to_auxiliary_dev(dev);
 
-	auxiliary_device_uninit(adev);
-
 	kfree(adev);
 }
 
-- 
2.39.2