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[169.235.26.60]) by smtp.gmail.com with ESMTPSA id o10-20020a4abe8a000000b004a0ad937ccdsm8281508oop.1.2022.12.29.22.36.00 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Dec 2022 22:36:01 -0800 (PST) From: Hang Zhang Cc: Daniel Vetter , Helge Deller , Javier Martinez Canillas , Thomas Zimmermann , Sam Ravnborg , Alex Deucher , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Hang Zhang Subject: [PATCH] fbmem: prevent potential use-after-free issues with console_lock() Date: Thu, 29 Dec 2022 22:35:28 -0800 Message-Id: <20221230063528.41037-1-zh.nvgt@gmail.com> X-Mailer: git-send-email 2.39.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org In do_fb_ioctl(), user specified "fb_info" can be freed in the callee fbcon_get_con2fb_map_ioctl() -> set_con2fb_map() -> con2fb_release_oldinfo(), this free operation is protected by console_lock() in fbcon_set_con2fb_map_ioctl(), it also results in the change of certain states such as "minfo->dead" in matroxfb_remove(), so that it can be checked to avoid use-after-free before the use sites (e.g., the check at the beginning of matroxfb_ioctl()). However, the problem is that the use site is not protected by the same locks as for the free operation, e.g., "default" case in do_fb_ioctl() can lead to "matroxfb_ioctl()" but it's not protected by console_lock(), which can invalidate the aforementioned state set and check in a concurrent setting. Prevent the potential use-after-free issues by protecting the "default" case in do_fb_ioctl() with console_lock(), similarly as for many other cases like "case FBIOBLANK" and "case FBIOPAN_DISPLAY". Signed-off-by: Hang Zhang --- drivers/video/fbdev/core/fbmem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 1e70d8c67653..8b1a1527d18a 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1182,6 +1182,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, console_unlock(); break; default: + console_lock(); lock_fb_info(info); fb = info->fbops; if (fb->fb_ioctl) @@ -1189,6 +1190,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, else ret = -ENOTTY; unlock_fb_info(info); + console_unlock(); } return ret; } -- 2.39.0 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 64168C46467 for ; Sat, 31 Dec 2022 14:30:23 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C762310E11F; Sat, 31 Dec 2022 14:30:05 +0000 (UTC) Received: from mail-oa1-x31.google.com (mail-oa1-x31.google.com [IPv6:2001:4860:4864:20::31]) by gabe.freedesktop.org (Postfix) with ESMTPS id CD03E10E067 for ; Fri, 30 Dec 2022 06:36:02 +0000 (UTC) Received: by mail-oa1-x31.google.com with SMTP id 586e51a60fabf-15027746720so8881309fac.13 for ; Thu, 29 Dec 2022 22:36:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=GAvkJUoPDYmWRhAwgSj95u5byto+2nWkIpy69HcVzzA=; b=chmxPcmZDfrqDkOb6grw5n9WABwC7AWm9NlE1JDaiZZVXSjJ0sTBOCA65G6ANggrp4 vZhXEMQwEMhw1TnKRlDtIz2+9kmySb60qBl9lliQwjy225K7qGxeKyjp17ocxLHj21F1 WjWW/Keir209f60myxHUh3MLgunDT8F4a6B3p7bRkTPDvWCyBqQMOovUxaJ3B/fIg1/x QwTtfarB29BSW6+WY9me3g666RVfvCG3JXyF4K3VOZPdLEX85petPfRFz7tcAy9WXG6G kz6aEl4nTZwiwAMyjwk6erNtMiqGF4ANOl62eqOcqxiaxWTaz2bhHAZ8gjLkhsiz+bnN E9yQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=GAvkJUoPDYmWRhAwgSj95u5byto+2nWkIpy69HcVzzA=; b=HTFokjdJY9r4qYZOfqzvwqVMvrPv9O0pkT8D540piHWjsN0hNXTmEZq95nv8BHN5L1 3m2ZGuBhn1mMcEiK76V1s9K+kvvpR6ozRBh8W2z3i4OJox+n2ePIEDK2q0tOhpCXWPVu QfVVD+TdsBF3p8kF2yLThTRJA6Igl/ZMu8hkKI1uYwueLcWbENLBqiVIo/D4vW5R6HWV JBaETOBeu2sd72tW4y9097cQBs3NL4fU7FiSYMsNs93xfaa0ZxM3JeywxuPr7vVS4koI tuflFD6nEouwGPDM0w6jXdAbeW0VDJgbCwKM/cODilFBTX47Vt6E9A3JRw5um74BPTl1 hvwQ== X-Gm-Message-State: AFqh2kqfX91zjoVjnJpafB6uP08FqDE2zb3hYZ1cP0EqGhZtW1I2QK+l qawS9z1TdDYyw4t5/Yg6tGo= X-Google-Smtp-Source: AMrXdXu8tuII+NQ94TSjxHteZaU5UKVhWyRIdtPSP8n4vzqiJe3EBkB9K95dp/oEC/QKGMbL8PYeng== X-Received: by 2002:a05:6870:be85:b0:144:4c04:4b73 with SMTP id nx5-20020a056870be8500b001444c044b73mr15306401oab.50.1672382161887; Thu, 29 Dec 2022 22:36:01 -0800 (PST) Received: from protoss.cs.ucr.edu (protoss.cs.ucr.edu. [169.235.26.60]) by smtp.gmail.com with ESMTPSA id o10-20020a4abe8a000000b004a0ad937ccdsm8281508oop.1.2022.12.29.22.36.00 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 29 Dec 2022 22:36:01 -0800 (PST) From: Hang Zhang To: Subject: [PATCH] fbmem: prevent potential use-after-free issues with console_lock() Date: Thu, 29 Dec 2022 22:35:28 -0800 Message-Id: <20221230063528.41037-1-zh.nvgt@gmail.com> X-Mailer: git-send-email 2.39.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Sat, 31 Dec 2022 14:30:00 +0000 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: linux-fbdev@vger.kernel.org, Hang Zhang , Helge Deller , Javier Martinez Canillas , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Thomas Zimmermann , Alex Deucher , Sam Ravnborg Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" In do_fb_ioctl(), user specified "fb_info" can be freed in the callee fbcon_get_con2fb_map_ioctl() -> set_con2fb_map() -> con2fb_release_oldinfo(), this free operation is protected by console_lock() in fbcon_set_con2fb_map_ioctl(), it also results in the change of certain states such as "minfo->dead" in matroxfb_remove(), so that it can be checked to avoid use-after-free before the use sites (e.g., the check at the beginning of matroxfb_ioctl()). However, the problem is that the use site is not protected by the same locks as for the free operation, e.g., "default" case in do_fb_ioctl() can lead to "matroxfb_ioctl()" but it's not protected by console_lock(), which can invalidate the aforementioned state set and check in a concurrent setting. Prevent the potential use-after-free issues by protecting the "default" case in do_fb_ioctl() with console_lock(), similarly as for many other cases like "case FBIOBLANK" and "case FBIOPAN_DISPLAY". Signed-off-by: Hang Zhang --- drivers/video/fbdev/core/fbmem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 1e70d8c67653..8b1a1527d18a 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1182,6 +1182,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, console_unlock(); break; default: + console_lock(); lock_fb_info(info); fb = info->fbops; if (fb->fb_ioctl) @@ -1189,6 +1190,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, else ret = -ENOTTY; unlock_fb_info(info); + console_unlock(); } return ret; } -- 2.39.0