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 3380B67752 for ; Thu, 4 Apr 2024 08:23:55 +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=1712219035; cv=none; b=YZoDd1mXDdayMCtfZm9IeW1Vp9AwXL8QbQbrOLdeb11mzxnAqlDAfR+UTfV5uUYgWACUeRuecJzMDjYMPldGz22r0O3uhrmbT2xzuHaXQGsAcV7rBw+pokIrpCSqKbyecmf3/0sLcnBlokev5RwjyU4ooZrwURcjFMGFrKJK4QQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712219035; c=relaxed/simple; bh=aESZUt8C+dxFXEIJ5H2vJVcIZQ3MBt6zidFlrySaKsM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=p7dlcWSOAYnDuYsEjmiUO7Za1lCtJCBMkxt7GVIvd0kp8QxYs7bzE5bs2aI6gHHg6fIkg2YMvpK1V+ub/0v5hu6Mk1aOvdpvvw9XSligSNUNRx29Vt9H8ybPzc5x5jiDBD45EIoTlV+xABcUXyyog3zMhYlYchkyvIMtkGOzW+U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1DxTt5QC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1DxTt5QC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94130C433F1; Thu, 4 Apr 2024 08:23:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712219035; bh=aESZUt8C+dxFXEIJ5H2vJVcIZQ3MBt6zidFlrySaKsM=; h=From:To:Cc:Subject:Date:Reply-to:From; b=1DxTt5QChegp4vzhzHLFEaqGQDWJrSDdmWniWHG2DWncc0vNWdM8AV2jFRZMV9UqE 3Y6AkPSkuLwx49y2/ePPtmGKeGBTD2zoK5VOn4O7Ojw5ZW8av735+3n5qHAPOKFnVk x2SAIcjRjLhMDGGj+9LnpudRdwDRlIkPrzEXYEsc= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2024-26798: fbcon: always restore the old font data in fbcon_do_set_font() Date: Thu, 4 Apr 2024 10:23:15 +0200 Message-ID: <2024040402-CVE-2024-26798-191e@gregkh> X-Mailer: git-send-email 2.44.0 Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Reply-to: , X-Developer-Signature: v=1; a=openpgp-sha256; l=3965; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=aESZUt8C+dxFXEIJ5H2vJVcIZQ3MBt6zidFlrySaKsM=; b=owGbwMvMwCRo6H6F97bub03G02pJDGl8yWmK/0O4vXdsy2XwX9Nk8aL/Wc7MkwX94RWWxRdzU uU26a/uiGVhEGRikBVTZPmyjefo/opDil6Gtqdh5rAygQxh4OIUgInclGGYH/8nReyD37ENYtXe sQJTX7asPpMRzTBXfEfjEcPVi29sDdp9wH6SSs7/9bY6AA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit Description =========== In the Linux kernel, the following vulnerability has been resolved: fbcon: always restore the old font data in fbcon_do_set_font() Commit a5a923038d70 (fbdev: fbcon: Properly revert changes when vc_resize() failed) started restoring old font data upon failure (of vc_resize()). But it performs so only for user fonts. It means that the "system"/internal fonts are not restored at all. So in result, the very first call to fbcon_do_set_font() performs no restore at all upon failing vc_resize(). This can be reproduced by Syzkaller to crash the system on the next invocation of font_get(). It's rather hard to hit the allocation failure in vc_resize() on the first font_set(), but not impossible. Esp. if fault injection is used to aid the execution/failure. It was demonstrated by Sirius: BUG: unable to handle page fault for address: fffffffffffffff8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD cb7b067 P4D cb7b067 PUD cb7d067 PMD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 8007 Comm: poc Not tainted 6.7.0-g9d1694dc91ce #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:fbcon_get_font+0x229/0x800 drivers/video/fbdev/core/fbcon.c:2286 Call Trace: con_font_get drivers/tty/vt/vt.c:4558 [inline] con_font_op+0x1fc/0xf20 drivers/tty/vt/vt.c:4673 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline] vt_ioctl+0x632/0x2ec0 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x6f8/0x1570 drivers/tty/tty_io.c:2803 vfs_ioctl fs/ioctl.c:51 [inline] ... So restore the font data in any case, not only for user fonts. Note the later 'if' is now protected by 'old_userfont' and not 'old_data' as the latter is always set now. (And it is supposed to be non-NULL. Otherwise we would see the bug above again.) The Linux kernel CVE team has assigned CVE-2024-26798 to this issue. Affected and fixed versions =========================== Issue introduced in 5.15.64 with commit ebd6f886aa24 and fixed in 5.15.151 with commit 20a4b5214f7b Issue introduced in 6.0 with commit a5a923038d70 and fixed in 6.1.81 with commit 2f91a96b892f Issue introduced in 6.0 with commit a5a923038d70 and fixed in 6.6.21 with commit 73a6bd68a134 Issue introduced in 6.0 with commit a5a923038d70 and fixed in 6.7.9 with commit a2c881413dcc Issue introduced in 6.0 with commit a5a923038d70 and fixed in 6.8 with commit 00d6a284fcf3 Issue introduced in 5.19.6 with commit f08ccb792d3e Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2024-26798 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/video/fbdev/core/fbcon.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/20a4b5214f7bee13c897477168c77bbf79683c3d https://git.kernel.org/stable/c/2f91a96b892fab2f2543b4a55740c5bee36b1a6b https://git.kernel.org/stable/c/73a6bd68a1342f3a44cac9dffad81ad6a003e520 https://git.kernel.org/stable/c/a2c881413dcc5d801bdc9535e51270cc88cb9cd8 https://git.kernel.org/stable/c/00d6a284fcf3fad1b7e1b5bc3cd87cbfb60ce03f