From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756554AbcEXR7D (ORCPT ); Tue, 24 May 2016 13:59:03 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:38006 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965089AbcEXR4Z (ORCPT ); Tue, 24 May 2016 13:56:25 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Jann Horn , Linus Torvalds , "David S . Miller" , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 40/53] bpf: fix double-fdput in replace_map_fd_with_map_ptr() Date: Tue, 24 May 2016 10:55:10 -0700 Message-Id: <1464112523-3701-41-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1464112523-3701-1-git-send-email-kamal@canonical.com> References: <1464112523-3701-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt11 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Jann Horn [ Upstream commit 8358b02bf67d3a5d8a825070e1aa73f25fb2e4c7 ] 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 Signed-off-by: David S. Miller Signed-off-by: Kamal Mostafa --- kernel/bpf/verifier.c | 1 - 1 file changed, 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b1f68c2..9718319 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1896,7 +1896,6 @@ 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); } -- 2.7.4