From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from madrid.collaboradmins.com (madrid.collaboradmins.com [46.235.227.194]) (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 E5850339BC for ; Fri, 17 May 2024 11:09:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=46.235.227.194 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715944180; cv=none; b=p1Tpc2jf5XCYSGWLbIghuDpAl0tD3OjdMRtayAJi7di+OsQ6N4hpwDFkof6fuScGmMqD37MUMeYIb+fMkWdoBQyMjQxLp0+gUZcJOSZA80M0w0MX6exolNAqaIQAsP322k/Xf5N2ypU3UegenRwbGBerRCu11OdhQ4J/xMNn3G8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715944180; c=relaxed/simple; bh=OgjgRDVDsrKTTU1Gi1fg62yVJMn/DK0OzAErludZMeo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FZJaQgVzNgaMtxzJlSX7ePCAxqidXyeEg0QU9l8ozVO4f6jyPxepSRyv9yma1mD7mqQ5u2/9gGDk7YtafkTHaYFoQBQep9LuEiAaDN2yS3yy8vWi3FhxULUv5yNxOUcGezje89mlV0ErQsnkn3Vjcn4AUoiOXzJbZ0/gr5IuTW0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=yEouNVPc; arc=none smtp.client-ip=46.235.227.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="yEouNVPc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1715944177; bh=OgjgRDVDsrKTTU1Gi1fg62yVJMn/DK0OzAErludZMeo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=yEouNVPcBZFKAhWQDyw5oCjcE9frfth6/kaO3NGegFTBDMjqZlxXKZaM7dp3Ftyny SJdL8ZjyPCdpMj0Enk9TZWz9SRaZScU10DAWVjnIVNq4m+C+rpU0nTgce99HqppYGW ABR/wmbIaMsk7M3ocu/FSSA50osWG6QBNXWQcdJjMumaUT9eEa0CPY+F7vsHXCwDlS n12gtfhTnmHfhLEvo77DXAzHrn9C+g4LTkfdMTv1rLT7qH0q0a17fHSg4vQoNrZds1 f+gGTJLo8bUHX5u9A2thq+WmbMnuhCkC++SaVrXFZhoYDcX6qoKEskv3a66PqlNGqp qWSZk5JB7BU+w== Received: from [100.113.186.2] (cola.collaboradmins.com [195.201.22.229]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: kholk11) by madrid.collaboradmins.com (Postfix) with ESMTPSA id 6A4313781116; Fri, 17 May 2024 11:09:36 +0000 (UTC) Message-ID: <0d8f89d4-e16e-4c8d-b983-38df8fcc387e@collabora.com> Date: Fri, 17 May 2024 13:09:35 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/mediatek/dp: fix spurious kfree() To: Michael Walle , Chun-Kuang Hu , Philipp Zabel , David Airlie , Daniel Vetter , Matthias Brugger Cc: Jani Nikula , Chen-Yu Tsai , linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20240517093024.1702750-1-mwalle@kernel.org> From: AngeloGioacchino Del Regno Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Il 17/05/24 13:07, Michael Walle ha scritto: > On Fri May 17, 2024 at 12:35 PM CEST, AngeloGioacchino Del Regno wrote: >> Il 17/05/24 11:30, Michael Walle ha scritto: >>> drm_edid_to_sad() might return an error or just zero. If that is the >>> case, we must not free the SADs because there was no allocation in >>> the first place. >>> >>> Fixes: dab12fa8d2bd ("drm/mediatek/dp: fix memory leak on ->get_edid callback audio detection") >>> Signed-off-by: Michael Walle >>> --- >>> drivers/gpu/drm/mediatek/mtk_dp.c | 10 ++++++++-- >>> 1 file changed, 8 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c >>> index 536366956447..ada12927bbac 100644 >>> --- a/drivers/gpu/drm/mediatek/mtk_dp.c >>> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c >>> @@ -2073,9 +2073,15 @@ static const struct drm_edid *mtk_dp_edid_read(struct drm_bridge *bridge, >>> */ >>> const struct edid *edid = drm_edid_raw(drm_edid); >>> struct cea_sad *sads; >>> + int ret; >>> >>> - audio_caps->sad_count = drm_edid_to_sad(edid, &sads); >>> - kfree(sads); >>> + ret = drm_edid_to_sad(edid, &sads); >>> + /* Ignore any errors */ >>> + if (ret < 0) >>> + ret = 0; >>> + if (ret) >> >> Eh, this will never work, because you're clearing the error before checking >> if there's any error here?!?! :-P > > Don't get what you mean? Yes, I'm ignoring the error. Thus, in case > of an error ret will be zero and there will be no free. If ret was > zero, there won't be a free either. So you're left with the "normal" > case, where you have to free the sads. Just like before. > >> Anyway in reality, it returns -ENOMEM if the allocation was not successful... >> in the event that any future update adds any other error we'd be back with the same >> issue, but I'm not sure how much should we worry about that. >> >> To be extremely safe, we could do... >> >> if (ret != -ENOMEM) >> kfree(sads) >> >> audio_caps->sad_count = ret < 0 ? 0 : ret; > > Which is the same as above, but you only check for ENOMEM? > Yes, the point is to avoid kfree(sads) for -ENOMEM only, as other errors that may be introduced later might still allocate it and leave it allocated. > -michael > >> >> Cheers! >> Angelo >> >>> + kfree(sads); >>> + audio_caps->sad_count = ret; >>> >>> /* >>> * FIXME: This should use connector->display_info.has_audio from >