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 E741F64AB0; Tue, 23 Jan 2024 01:57:33 +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=1705975054; cv=none; b=gbOsdFfjBsxStjuHM4qkOcuNw8fEC7NVE69CWmT0ciM66IqpWsrx/H+GfgEvLtt8dE7TWFuAFg60yJKkmOh00rs8VUVhHfMrhAyQUBWXPmaMhAfRFCrPtks4kqS6oZc9TJXR/1K/7KYjP5a22j9/FceFt5DGk/CK1iT+OKfdQtA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705975054; c=relaxed/simple; bh=5r2z2HeRP/WhLTxa+enQC853bz6Go9lHd1MB8nLtN4c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Wad4lMpmqYOWpGYnhZ2G0rSVB5N4OIi7Ze1Smrfn/vGpuF/UWMJc4MF4q/ScGFsMJjo2oLMNGwUULq1FEl70BGoS5AwSGLhPu9lr8aJFvpgkfuUOUgqiEjrpNCYcQPmyD5jV+PSxtpuNLXxoGt48Xy5DQYSZDRoL7LAwSBIAJkU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GHMU7cdW; 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="GHMU7cdW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9C60C433C7; Tue, 23 Jan 2024 01:57:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1705975053; bh=5r2z2HeRP/WhLTxa+enQC853bz6Go9lHd1MB8nLtN4c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GHMU7cdWCPmoNBn16ePcCp4LeScInkCm+0dU0UlJ/3m5l9g5pKxAx5hEG/R7/IEpY mglHpnfCU6dZ0HwY9L9XxZ/uzr9AkaPNmGTi66ThbG4Ee4aki/9hk+ZcyqIz818p4Y txnLA+bRWrBnfFlhiPyAWR0ADqTkG9uCZvwUlo1k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hao Sun , Daniel Borkmann , Yonghong Song , Sasha Levin Subject: [PATCH 5.15 342/374] bpf: Reject variable offset alu on PTR_TO_FLOW_KEYS Date: Mon, 22 Jan 2024 15:59:58 -0800 Message-ID: <20240122235756.819083650@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240122235744.598274724@linuxfoundation.org> References: <20240122235744.598274724@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hao Sun [ Upstream commit 22c7fa171a02d310e3a3f6ed46a698ca8a0060ed ] For PTR_TO_FLOW_KEYS, check_flow_keys_access() only uses fixed off for validation. However, variable offset ptr alu is not prohibited for this ptr kind. So the variable offset is not checked. The following prog is accepted: func#0 @0 0: R1=ctx() R10=fp0 0: (bf) r6 = r1 ; R1=ctx() R6_w=ctx() 1: (79) r7 = *(u64 *)(r6 +144) ; R6_w=ctx() R7_w=flow_keys() 2: (b7) r8 = 1024 ; R8_w=1024 3: (37) r8 /= 1 ; R8_w=scalar() 4: (57) r8 &= 1024 ; R8_w=scalar(smin=smin32=0, smax=umax=smax32=umax32=1024,var_off=(0x0; 0x400)) 5: (0f) r7 += r8 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r8 stack= before 4: (57) r8 &= 1024 mark_precise: frame0: regs=r8 stack= before 3: (37) r8 /= 1 mark_precise: frame0: regs=r8 stack= before 2: (b7) r8 = 1024 6: R7_w=flow_keys(smin=smin32=0,smax=umax=smax32=umax32=1024,var_off =(0x0; 0x400)) R8_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=1024, var_off=(0x0; 0x400)) 6: (79) r0 = *(u64 *)(r7 +0) ; R0_w=scalar() 7: (95) exit This prog loads flow_keys to r7, and adds the variable offset r8 to r7, and finally causes out-of-bounds access: BUG: unable to handle page fault for address: ffffc90014c80038 [...] Call Trace: bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline] __bpf_prog_run include/linux/filter.h:651 [inline] bpf_prog_run include/linux/filter.h:658 [inline] bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline] bpf_flow_dissect+0x15f/0x350 net/core/flow_dissector.c:991 bpf_prog_test_run_flow_dissector+0x39d/0x620 net/bpf/test_run.c:1359 bpf_prog_test_run kernel/bpf/syscall.c:4107 [inline] __sys_bpf+0xf8f/0x4560 kernel/bpf/syscall.c:5475 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline] __se_sys_bpf kernel/bpf/syscall.c:5559 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5559 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b Fix this by rejecting ptr alu with variable offset on flow_keys. Applying the patch rejects the program with "R7 pointer arithmetic on flow_keys prohibited". Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook") Signed-off-by: Hao Sun Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20240115082028.9992-1-sunhao.th@gmail.com Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c2ecf349523d..88a468cc0510 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7295,6 +7295,10 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, } switch (base_type(ptr_reg->type)) { + case PTR_TO_FLOW_KEYS: + if (known) + break; + fallthrough; case CONST_PTR_TO_MAP: /* smin_val represents the known value */ if (known && smin_val == 0 && opcode == BPF_ADD) -- 2.43.0