From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 363991E3DF7 for ; Tue, 17 Dec 2024 11:42:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734435769; cv=none; b=poQGJdv+LScb2G4xHAJttWjQ9pP3K0PXCSzeNy3KZziryAub/1jbtgEEUynd/mG7VRo5pXEYkE58IxMPJU5t5E18zK3pvt9D5EVYOUOEUjMjltjyUkkRClR22Uq8B4rQi0XsBtOuOakcb76moSAVOIWOP6lJcg93QE8Kx4Uez00= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734435769; c=relaxed/simple; bh=MUE7u9DBjXlKgzQucisF2XuBaVVftZfOahNhSetNR+I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ENO235Ek9bOUqcqDPAvRaeFV+VbE3A1qeSBK5GpLaWm9ZSB7L/gu8prLDgYynlLk9H+o31ZtNol9g4qsjFcBWFL1dq4LSVO/V2ZV47Bt7Ne/qOOY8qGPM8qO6sGa7nBadIxKn9pZtO3g9zC9Cv8Bg7foMMB6yVODfD3PttS+OdQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LGZaYXCH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="LGZaYXCH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5E7D9C4CED3; Tue, 17 Dec 2024 11:42:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1734435768; bh=MUE7u9DBjXlKgzQucisF2XuBaVVftZfOahNhSetNR+I=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=LGZaYXCHn4YBuc4GeRm+NLzdw8cMMJ5R0njTiJHiYFWNDWwjdETMhKvRdfKAMuuwn Bq/BUSv6GLlD9ycjL6cN2i66WFsAMnhtK7Th/7zaSNpz/lKmkb5QDpu8arQ8DbmNc3 uvPc++Rf8qQ1RuIp+tokqa5tmUh3YSKag/jTw9uJyJNUFcPrUcSuwliTI5q+3CUOWt j4WEg5WHsDOk7sIeuULlKF+Nn8rfM3IK1QVYTaSc6B5R7vvTGkEQOU/HP/bl1mRLFX nbSaOwhH1qT+OUUBbAxw4mzOcFpanQgcfinYQZBIIgEwc6kFu1GbxDcLz/AmFbd1Xm smCwwOUugNzXw== Message-ID: <1d5fa252-c43a-42de-8794-fecfaf90b71a@kernel.org> Date: Tue, 17 Dec 2024 12:42:44 +0100 Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] memory: tegra20-emc: fix an OF node reference bug in tegra_emc_find_node_by_ram_code() To: Joe Hattori , thierry.reding@gmail.com, jonathanh@nvidia.com Cc: linux-tegra@vger.kernel.org References: <20241217091434.1993597-1-joe@pf.is.s.u-tokyo.ac.jp> <80e21d04-75a4-4361-8623-0dbadcd4ff2a@kernel.org> Content-Language: en-US From: Krzysztof Kozlowski Autocrypt: addr=krzk@kernel.org; keydata= xsFNBFVDQq4BEAC6KeLOfFsAvFMBsrCrJ2bCalhPv5+KQF2PS2+iwZI8BpRZoV+Bd5kWvN79 cFgcqTTuNHjAvxtUG8pQgGTHAObYs6xeYJtjUH0ZX6ndJ33FJYf5V3yXqqjcZ30FgHzJCFUu JMp7PSyMPzpUXfU12yfcRYVEMQrmplNZssmYhiTeVicuOOypWugZKVLGNm0IweVCaZ/DJDIH gNbpvVwjcKYrx85m9cBVEBUGaQP6AT7qlVCkrf50v8bofSIyVa2xmubbAwwFA1oxoOusjPIE J3iadrwpFvsZjF5uHAKS+7wHLoW9hVzOnLbX6ajk5Hf8Pb1m+VH/E8bPBNNYKkfTtypTDUCj NYcd27tjnXfG+SDs/EXNUAIRefCyvaRG7oRYF3Ec+2RgQDRnmmjCjoQNbFrJvJkFHlPeHaeS BosGY+XWKydnmsfY7SSnjAzLUGAFhLd/XDVpb1Een2XucPpKvt9ORF+48gy12FA5GduRLhQU vK4tU7ojoem/G23PcowM1CwPurC8sAVsQb9KmwTGh7rVz3ks3w/zfGBy3+WmLg++C2Wct6nM Pd8/6CBVjEWqD06/RjI2AnjIq5fSEH/BIfXXfC68nMp9BZoy3So4ZsbOlBmtAPvMYX6U8VwD TNeBxJu5Ex0Izf1NV9CzC3nNaFUYOY8KfN01X5SExAoVTr09ewARAQABzSVLcnp5c3p0b2Yg S296bG93c2tpIDxrcnprQGtlcm5lbC5vcmc+wsGVBBMBCgA/AhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgBYhBJvQfg4MUfjVlne3VBuTQ307QWKbBQJgPO8PBQkUX63hAAoJEBuTQ307 QWKbBn8P+QFxwl7pDsAKR1InemMAmuykCHl+XgC0LDqrsWhAH5TYeTVXGSyDsuZjHvj+FRP+ gZaEIYSw2Yf0e91U9HXo3RYhEwSmxUQ4Fjhc9qAwGKVPQf6YuQ5yy6pzI8brcKmHHOGrB3tP /MODPt81M1zpograAC2WTDzkICfHKj8LpXp45PylD99J9q0Y+gb04CG5/wXs+1hJy/dz0tYy iua4nCuSRbxnSHKBS5vvjosWWjWQXsRKd+zzXp6kfRHHpzJkhRwF6ArXi4XnQ+REnoTfM5Fk VmVmSQ3yFKKePEzoIriT1b2sXO0g5QXOAvFqB65LZjXG9jGJoVG6ZJrUV1MVK8vamKoVbUEe 0NlLl/tX96HLowHHoKhxEsbFzGzKiFLh7hyboTpy2whdonkDxpnv/H8wE9M3VW/fPgnL2nPe xaBLqyHxy9hA9JrZvxg3IQ61x7rtBWBUQPmEaK0azW+l3ysiNpBhISkZrsW3ZUdknWu87nh6 eTB7mR7xBcVxnomxWwJI4B0wuMwCPdgbV6YDUKCuSgRMUEiVry10xd9KLypR9Vfyn1AhROrq AubRPVeJBf9zR5UW1trJNfwVt3XmbHX50HCcHdEdCKiT9O+FiEcahIaWh9lihvO0ci0TtVGZ MCEtaCE80Q3Ma9RdHYB3uVF930jwquplFLNF+IBCn5JRzsFNBFVDXDQBEADNkrQYSREUL4D3 Gws46JEoZ9HEQOKtkrwjrzlw/tCmqVzERRPvz2Xg8n7+HRCrgqnodIYoUh5WsU84N03KlLue MNsWLJBvBaubYN4JuJIdRr4dS4oyF1/fQAQPHh8Thpiz0SAZFx6iWKB7Qrz3OrGCjTPcW6ei OMheesVS5hxietSmlin+SilmIAPZHx7n242u6kdHOh+/SyLImKn/dh9RzatVpUKbv34eP1wA GldWsRxbf3WP9pFNObSzI/Bo3kA89Xx2rO2roC+Gq4LeHvo7ptzcLcrqaHUAcZ3CgFG88CnA 6z6lBZn0WyewEcPOPdcUB2Q7D/NiUY+HDiV99rAYPJztjeTrBSTnHeSBPb+qn5ZZGQwIdUW9 YegxWKvXXHTwB5eMzo/RB6vffwqcnHDoe0q7VgzRRZJwpi6aMIXLfeWZ5Wrwaw2zldFuO4Dt 91pFzBSOIpeMtfgb/Pfe/a1WJ/GgaIRIBE+NUqckM+3zJHGmVPqJP/h2Iwv6nw8U+7Yyl6gU BLHFTg2hYnLFJI4Xjg+AX1hHFVKmvl3VBHIsBv0oDcsQWXqY+NaFahT0lRPjYtrTa1v3tem/ JoFzZ4B0p27K+qQCF2R96hVvuEyjzBmdq2esyE6zIqftdo4MOJho8uctOiWbwNNq2U9pPWmu 4vXVFBYIGmpyNPYzRm0QPwARAQABwsF8BBgBCgAmAhsMFiEEm9B+DgxR+NWWd7dUG5NDfTtB YpsFAmA872oFCRRflLYACgkQG5NDfTtBYpvScw/9GrqBrVLuJoJ52qBBKUBDo4E+5fU1bjt0 Gv0nh/hNJuecuRY6aemU6HOPNc2t8QHMSvwbSF+Vp9ZkOvrM36yUOufctoqON+wXrliEY0J4 ksR89ZILRRAold9Mh0YDqEJc1HmuxYLJ7lnbLYH1oui8bLbMBM8S2Uo9RKqV2GROLi44enVt vdrDvo+CxKj2K+d4cleCNiz5qbTxPUW/cgkwG0lJc4I4sso7l4XMDKn95c7JtNsuzqKvhEVS oic5by3fbUnuI0cemeizF4QdtX2uQxrP7RwHFBd+YUia7zCcz0//rv6FZmAxWZGy5arNl6Vm lQqNo7/Poh8WWfRS+xegBxc6hBXahpyUKphAKYkah+m+I0QToCfnGKnPqyYIMDEHCS/RfqA5 t8F+O56+oyLBAeWX7XcmyM6TGeVfb+OZVMJnZzK0s2VYAuI0Rl87FBFYgULdgqKV7R7WHzwD uZwJCLykjad45hsWcOGk3OcaAGQS6NDlfhM6O9aYNwGL6tGt/6BkRikNOs7VDEa4/HlbaSJo 7FgndGw1kWmkeL6oQh7wBvYll2buKod4qYntmNKEicoHGU+x91Gcan8mCoqhJkbqrL7+nXG2 5Q/GS5M9RFWS+nYyJh+c3OcfKqVcZQNANItt7+ULzdNJuhvTRRdC3g9hmCEuNSr+CLMdnRBY fv0= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 17/12/2024 12:07, Joe Hattori wrote: > > > On 12/17/24 18:31, Krzysztof Kozlowski wrote: >> On 17/12/2024 10:14, Joe Hattori wrote: >>> As of_find_node_by_name() release the reference of the given OF node, >> >> No, it does not. > > I see in the document of the of_find_node_by_name() says that it calls > of_node_put(), or am I looking at the wrong code? Hm, that's true that reference is put, but on the input node, not returned one. I don't get to which node you are referring here thus which node has double release or use-after-release. Maybe it is all about incorrect dropping of this device's device node, which should never happen in driver's probe path? > /** > * of_find_node_by_name - Find a node by its "name" property > * @from: The node to start searching from or NULL; the node > * you pass will not be searched, only the next one > * will. Typically, you pass what the previous call > * returned. of_node_put() will be called on @from. > * @name: The name string to match against > * > * Return: A node pointer with refcount incremented, use > * of_node_put() on it when done. > */ > > >> >>> tegra_emc_find_node_by_ram_code() releases some OF nodes while still in >>> use, resulting in possible UAFs. Given the DT structure, utilize the >>> for_each_child_of_node macro and of_get_child_by_name() to avoid the bug. >>> >>> This bug was found by an experimental verification tool that I am >>> developing. >>> >>> Fixes: 96e5da7c8424 ("memory: tegra: Introduce Tegra20 EMC driver") >>> Signed-off-by: Joe Hattori >>> --- >>> drivers/memory/tegra/tegra20-emc.c | 8 ++++---- >>> 1 file changed, 4 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/memory/tegra/tegra20-emc.c b/drivers/memory/tegra/tegra20-emc.c >>> index 7193f848d17e..9b7d30a21a5b 100644 >>> --- a/drivers/memory/tegra/tegra20-emc.c >>> +++ b/drivers/memory/tegra/tegra20-emc.c >>> @@ -474,14 +474,15 @@ tegra_emc_find_node_by_ram_code(struct tegra_emc *emc) >>> >>> ram_code = tegra_read_ram_code(); >>> >>> - for (np = of_find_node_by_name(dev->of_node, "emc-tables"); np; >>> - np = of_find_node_by_name(np, "emc-tables")) { >>> + for_each_child_of_node(dev->of_node, np) { >> >> I don't understand how this change is related to described problem. > > As per the document, of_find_node_by_name() calls of_node_put(np), and In the first call no, it will of_node_put(from), not 'np'. 'from' != 'np'. > the current code is calling of_node_put() before continuing the loop, so > the np can be released twice. By the second release, you mean in the "if (cfg_mismatches)" path? Otherwise there is no second release in the for loop. > >> >>> + if (!of_node_name_eq(np, "emc-tables")) >>> + continue; >>> err = of_property_read_u32(np, "nvidia,ram-code", &value); >>> if (err || value != ram_code) { >>> struct device_node *lpddr2_np; >>> bool cfg_mismatches = false; >>> >>> - lpddr2_np = of_find_node_by_name(np, "lpddr2"); >>> + lpddr2_np = of_get_child_by_name(np, "lpddr2"); >> >> Why? > > Given the Devicetree structure, I understand that calling > of_get_child_by_name() suffices here, which also does not release the > reference of np. So you assume these have to be children. Is it tested with bindings? With actual device? > >> >>> if (lpddr2_np) { >>> const struct lpddr2_info *info; >>> >>> @@ -518,7 +519,6 @@ tegra_emc_find_node_by_ram_code(struct tegra_emc *emc) >>> } >>> >>> if (cfg_mismatches) { >>> - of_node_put(np); >> >> If of_find_node_by_name() drops reference, why this was needed > >>> continue; >> Best regards, Krzysztof