From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC5BFC47095 for ; Wed, 9 Jun 2021 09:22:01 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B66B46120F for ; Wed, 9 Jun 2021 09:22:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B66B46120F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3B5D26E09C; Wed, 9 Jun 2021 09:22:01 +0000 (UTC) Received: from mail-pg1-x535.google.com (mail-pg1-x535.google.com [IPv6:2607:f8b0:4864:20::535]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8FB846E09C for ; Wed, 9 Jun 2021 09:22:00 +0000 (UTC) Received: by mail-pg1-x535.google.com with SMTP id i34so12506831pgl.9 for ; Wed, 09 Jun 2021 02:22:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1HdeYeZU8aBbB01u3EptGGzTktTYXaU7YZzov/SDA8I=; b=b4EpkScIYTfhDr+1DMH9NGb/JEGCVMC9I0UEyR0v35fGLBQSlI8BS1JDdPwEi26sGQ KPb2AUw2GDSNvGJGPErFOeww/av+JYG7UmLiOxZgOlAggtefR5FUeMsoRoDKnhoHtI8u 0E0v05ydQAErk3dBnyG43LsFRo9bYbJkhu+NdLUfvu+vjlDoM3ZknsyBXJ9NjBDzpAcr HLBi/331j1metmaNnix8gGpxm82JMyR1mV18SJZWKZJpLxC2uTO8gup6tbgZ003q4Of5 MznuY50X/r972sJpUhon8MiAZUcUYmgfQTYatvtdKj6f1XI5znqAeyQ7060yHHdxWgGA rSvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1HdeYeZU8aBbB01u3EptGGzTktTYXaU7YZzov/SDA8I=; b=nMIKtxl2SqQ/M/zwJND0TsZ6kG6TnZAvonr74+Gh8UEgt8ZRyCc2HMuqRVY+c+L1N5 9WSbkbLTwr/vPcaLsTt36siY+XhQlcwAVIxnlcy2EyG8sqy4EMadcrLyRhUjAUYoYqnm qUi6NMot0KwFDiWvUKirovYJ1dGjzCkVZcBJaPsD+zUOZOQkqHZZyebM1U+6pjTSZhuD GzCItX08pUWBMiPsFqLl8UnWXcSat3N3ZSI4ELorXXUjYSbjXK/mGFAeVB3fghy4f5Zw 6/dA+dBzAQJ1MZIkEkADyZYjC+f38mLeoDJlSdts782dPP6CL1dgFBuIo0pe3me9zj4w Tmtw== X-Gm-Message-State: AOAM533bYQ64kBP6rslgfYKqW1B5CGtpiAwLe6xrYhPQ4Mwe1bBBSXRk mPI4jYGeLcNqcIQ92DojGek= X-Google-Smtp-Source: ABdhPJwJbjQpq27OslPPl05sK51n7VSNJg+Oy499gokZlzfdlXjo0kUTNl8b19jl4Y/n4hNDMlA3Ow== X-Received: by 2002:a65:4508:: with SMTP id n8mr2895991pgq.120.1623230520212; Wed, 09 Jun 2021 02:22:00 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id z22sm13793464pfa.157.2021.06.09.02.21.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 02:21:59 -0700 (PDT) From: Desmond Cheong Zhi Xi To: maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch Subject: [PATCH] drm: Lock pointer access in drm_master_release() Date: Wed, 9 Jun 2021 17:21:19 +0800 Message-Id: <20210609092119.173590-1-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, skhan@linuxfoundation.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org, Dan Carpenter Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This patch eliminates the following smatch warning: drivers/gpu/drm/drm_auth.c:320 drm_master_release() warn: unlocked access 'master' (line 318) expected lock '&dev->master_mutex' The 'file_priv->master' field should be protected by the mutex lock to '&dev->master_mutex'. This is because other processes can concurrently modify this field and free the current 'file_priv->master' pointer. This could result in a use-after-free error when 'master' is dereferenced in subsequent function calls to 'drm_legacy_lock_master_cleanup()' or to 'drm_lease_revoke()'. An example of a scenario that would produce this error can be seen from a similar bug in 'drm_getunique()' that was reported by Syzbot: https://syzkaller.appspot.com/bug?id=148d2f1dfac64af52ffd27b661981a540724f803 In the Syzbot report, another process concurrently acquired the device's master mutex in 'drm_setmaster_ioctl()', then overwrote 'fpriv->master' in 'drm_new_set_master()'. The old value of 'fpriv->master' was subsequently freed before the mutex was unlocked. Reported-by: Dan Carpenter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index f00e5abdbbf4..b59b26a71ad5 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -315,9 +315,10 @@ int drm_master_open(struct drm_file *file_priv) void drm_master_release(struct drm_file *file_priv) { struct drm_device *dev = file_priv->minor->dev; - struct drm_master *master = file_priv->master; + struct drm_master *master; mutex_lock(&dev->master_mutex); + master = file_priv->master; if (file_priv->magic) idr_remove(&file_priv->master->magic_map, file_priv->magic); -- 2.25.1