From patchwork Tue Apr 26 20:26:26 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jann Horn X-Patchwork-Id: 615237 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3qvZPW4p6kz9t4B for ; Wed, 27 Apr 2016 06:26:39 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.b=S/wW/kdn; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753939AbcDZU0f (ORCPT ); Tue, 26 Apr 2016 16:26:35 -0400 Received: from mail-wm0-f53.google.com ([74.125.82.53]:37758 "EHLO mail-wm0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753829AbcDZU0c (ORCPT ); Tue, 26 Apr 2016 16:26:32 -0400 Received: by mail-wm0-f53.google.com with SMTP id n3so21736116wmn.0 for ; Tue, 26 Apr 2016 13:26:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=from:to:cc:subject:date:message-id; bh=qJEK2AipWMogofkL+RoPwEa6YfXfQV2IAFzaOzj6B7s=; b=S/wW/kdn4z5Obg2NZBXEt4FAwdRCI0KSsWeLXvwLeGW6NhEN1eATzVc7UQEif8BxBs 1ep5RZj0WENWlIpUjAbrFky4sJ1efPoW+TGfA/wPr/eyJRHCG9pWweYFEPFVyR5EH8JA 9i+bUf9TXJy7z/ijLPtg3x9/qFZY785/fM/Zc53ZpoWBVXrFstRhutG9PsEoD4H1gdy4 FY0iM5vwG2KNmalrKHCbqRkNwgYoNoGvkCOdD7vgzAvNNcPxoDw77UM6S5ryZUHJTnt8 yuEGJBYatGBhA1QlO0AQPQVZkZ5MS9sN+A3Zvc6FyBSi1J0LKsIPrveQMMtpeLbadoad soCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=qJEK2AipWMogofkL+RoPwEa6YfXfQV2IAFzaOzj6B7s=; b=Kl+B6tBFZ/ZPWMAK6qHJXIiiqd4kZ5Ka33jJ/smvlY9zZz3u9HYaLcrAwKyqYuZqrv udNx9boe4zIZ7zouuuKEid74qeXJsHEtQCGNgi4ew3IhDEy+jrKFd0LNUcxjF8xhUFKl ppgFNPgDpVW1p6n24+KtkBhl0+vZweyiggMdHTHuWefj6KiLgOFS9i/kfw8wm1GrgTD/ 2lgblZmrTdNAecCOUaVGUJxc05uPHLxrPQscTT3WIDfYwJ8tncLRm12K+wP6lAccOYUn bbCiqUNte8AjYZuSTW0NKyYrs3cIw1nB3TkUAKrPLXLAEbPESnqMiBBFSU7sJaULXdg9 HeGA== X-Gm-Message-State: AOPr4FW9WlvqnnBLNiSLkffc+RJvm6ZrNEuyd/jaMRyY0dQRJHtLXe6nTD1Tr2IaTiGqd8uq X-Received: by 10.194.23.226 with SMTP id p2mr5154181wjf.131.1461702390829; Tue, 26 Apr 2016 13:26:30 -0700 (PDT) Received: from jannh.zrh.corp.google.com ([100.105.131.44]) by smtp.gmail.com with ESMTPSA id o4sm358993wjx.45.2016.04.26.13.26.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 26 Apr 2016 13:26:30 -0700 (PDT) From: Jann Horn To: David Miller Cc: netdev@vger.kernel.org, Jann Horn Subject: [PATCH] bpf: fix double-fdput in replace_map_fd_with_map_ptr() Date: Tue, 26 Apr 2016 22:26:26 +0200 Message-Id: <1461702386-17490-1-git-send-email-jannh@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org When bpf(BPF_PROG_LOAD, ...) was invoked with a BPF program whose bytecode references a non-map file descriptor as a map file descriptor, the error handling code called fdput() twice instead of once (in __bpf_map_get() and in replace_map_fd_with_map_ptr()). If the file descriptor table of the current task is shared, this causes f_count to be decremented too much, allowing the struct file to be freed while it is still in use (use-after-free). This can be exploited to gain root privileges by an unprivileged user. This bug was introduced in commit 0246e64d9a5f ("bpf: handle pseudo BPF_LD_IMM64 insn"), but is only exploitable since commit 1be7f75d1668 ("bpf: enable non-root eBPF programs") because previously, CAP_SYS_ADMIN was required to reach the vulnerable code. (posted publicly according to request by maintainer) Signed-off-by: Jann Horn Signed-off-by: Linus Torvalds Acked-by: Alexei Starovoitov Acked-by: Daniel Borkmann --- kernel/bpf/verifier.c | 1 - 1 file changed, 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2e08f8e..8291251 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2029,7 +2029,6 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env) if (IS_ERR(map)) { verbose("fd %d is not pointing to valid bpf_map\n", insn->imm); - fdput(f); return PTR_ERR(map); }