From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f46.google.com (mail-ej1-f46.google.com [209.85.218.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E03511AAE0F for ; Thu, 20 Jun 2024 10:27:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718879228; cv=none; b=m3YyE35IN0szeoXbexj4vi4/AtfnLW4MbGJGvY0/y+6MJfxYtwSBFpTq2sn3FPwBGZTFqrQ+nXAis3N0FBRWprXOZKXbi9zgFa3yQUXFLSdhlrOaKPG1O0n6Cq5zxjak6YQMOsqBvWBArV8kT2GDsJxmKxknr95ddh18Csya0q0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718879228; c=relaxed/simple; bh=nbP+Bhd4Oz50eEYww49+b2pyQ5OQncxkrW0NyGylRy4=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZRQcarB7Qg2nt4txq1B5TSGdUWJnj5acdpn/FcMqePsrvvU14QyjHIhO8J8Nm00c0wqgR2cRPPFs9TX2kgRfwHrtMKhQgRqBK1jBmNqJMKoFBKflpVXOSFZDU7RVntrjeM4Tw2PEm8C7hOEKhLj8NDIUwhdj+RC1HHYjaNY+UfM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Zmv8axE9; arc=none smtp.client-ip=209.85.218.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Zmv8axE9" Received: by mail-ej1-f46.google.com with SMTP id a640c23a62f3a-a6e43dad8ecso124615966b.1 for ; Thu, 20 Jun 2024 03:27:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1718879225; x=1719484025; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=WunkOUBrHfnw8piozH8R3AlMLN+JNYbl5dNpHNSKR7w=; b=Zmv8axE94tzWomGemADl5lQRX2Mu/wfGrcUMxK2o9NxTCuiT2ZqktehIFspjzRHfR3 yV7dLxTKd256PjMbZajl/e3q+h0CvUIntYN3bMhQKmuAQqMWR7HFwYOZxpmQOKf3zbqW stM6V6R9ulGhjKHe4+lcMG2gDV3+SvE6SGsbpwWAUhNsTn3tGdJzbifM54Y57knim7GT Ca8lzxgv7EXay9LetxTcfghCOpoeKHCD5GMaIbzgc+iy/JZlSgSXrklzewNURGb+254r akzyYPNuKB28Iimh0ZAKgVKopGfT/w+fJMnEmqNO+yCzhKpLznvH9HkXCRNcRCjv1Zoy ci/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718879225; x=1719484025; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=WunkOUBrHfnw8piozH8R3AlMLN+JNYbl5dNpHNSKR7w=; b=TtR0tGVwjGt+TvMxV56SB8da3zE/RG64YWrYCQ8xf5iOQ3KhMW1D3065TMC6tlYiqG 5ETy9asI+3lNBLhxmpiIy7KFOhbd4w5tOAa9VDi8+gNk5m5gECJ7zKGr/iLrbJ8s0eQd kD5Z+2ijNVW2p1knOQX3h8q3jfxva/PS/+18RXmgVUJls+IElaR53X9OqySiIVl8VfuC saFckMLqewBrOMEc6JF8Qfcqn+nPDYDJdvVULOKS1tLdeKVy+jvKW+WKJzTNBNKfIaHM 9vzQLABRxYRHUUv93OUt0/0FjagdSzX3ksZfo3SdEI3WBxTArCDSJHDKLU/nE/es3ylb aMIA== X-Forwarded-Encrypted: i=1; AJvYcCXy8A6b0RrH/iYW8DVGacBhXZnIzuhjD1WKh/xXg2HkvRvuc6OxdQ2M+ET/rccxKi0p5b7+XuHSZp/SaipzKT4XX0qi X-Gm-Message-State: AOJu0YwPp8s5eMFxArXKEFkQr9bZb2QMpX4APtk9aMIvn2Td4dJxVMum G9UFU+OPBYQAUotNZP4wo8PF/igDU8jJkCNNI9D/Bbz2GFa98v4O X-Google-Smtp-Source: AGHT+IH8thtGPzLz/4Nvvx+Z0CNBRzF3zcJOlqEMrL09YKxqNbg9hMNJeJV1sqr0wB+isH2eNQQdZQ== X-Received: by 2002:a17:907:d406:b0:a6f:b3d3:fed1 with SMTP id a640c23a62f3a-a6fb3d3ff9amr315541866b.10.1718879224903; Thu, 20 Jun 2024 03:27:04 -0700 (PDT) Received: from krava (2001-1ae9-1c2-4c00-726e-c10f-8833-ff22.ip6.tmcz.cz. [2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a6f56f41684sm752079666b.153.2024.06.20.03.27.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Jun 2024 03:27:04 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 20 Jun 2024 12:27:02 +0200 To: Tengda Wu Cc: Leon Hwang , bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo Subject: Re: [PATCH bpf] bpf: Fix null pointer dereference in resolve_prog_type() for BPF_PROG_TYPE_EXT Message-ID: References: <20240620060701.1465291-1-wutengda@huaweicloud.com> <2c5d2fdb-19ee-4b3c-9004-5e4d0a8719b8@huaweicloud.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2c5d2fdb-19ee-4b3c-9004-5e4d0a8719b8@huaweicloud.com> On Thu, Jun 20, 2024 at 04:54:51PM +0800, Tengda Wu wrote: > > > On 2024/6/20 14:46, Leon Hwang wrote: > > > > > > On 20/6/24 14:07, Tengda Wu wrote: > >> When loading a EXT program without specifying `attr->attach_prog_fd`, > >> the `prog->aux->dst_prog` will be null. At this time, calling > >> resolve_prog_type() anywhere will result in a null pointer dereference. > > > > Interesting, same NULL pointer dereference causes another issue[0]. > > > > As for my case, when resolve_prog_type(), it has to use > > prog->aux->saved_dst_prog_type instead of prog->aux->dst_prog->type for > > EXT program, in order to avoid NULL pointer dereference. > > > > [0] https://lore.kernel.org/bpf/20240602122421.50892-2-hffilwlqm@gmail.com/ > > > > Thanks, > > Leon > >This looks good, but unfortunately, there is still a problem with using > `prog->aux->saved_dst_prog_type` to resolve prog type, because its value still > comes from `prog->aux->dst_prog`in check_attach_btf_id(). > > Additionally, resolve_prog_type() not always be used after check_attach_btf_id(). > The following example stack trace proves the existence of this situation. It > shows that NULL pointer dereference occurs in add_subprog_and_kfunc(), which > check_attach_btf_id() has not yet reached. > > So it may be more effective to check and avoid dst_prog empty when EXT program loads. also please note it's breaking test_libbpf_probe_prog_types test test_libbpf_probe_prog_types:FAIL:BPF_PROG_TYPE_EXT unexpected BPF_PROG_TYPE_EXT: actual 0 != expected 1 because the attach_prog_fd wasn't needed to load EXT program before, but I guess the following attach would fail.. so it's likely ok jirka > > >> > >> Example stack trace: > >> > >> [ 8.107863] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004 > >> [ 8.108262] Mem abort info: > >> [ 8.108384] ESR = 0x0000000096000004 > >> [ 8.108547] EC = 0x25: DABT (current EL), IL = 32 bits > >> [ 8.108722] SET = 0, FnV = 0 > >> [ 8.108827] EA = 0, S1PTW = 0 > >> [ 8.108939] FSC = 0x04: level 0 translation fault > >> [ 8.109102] Data abort info: > >> [ 8.109203] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 > >> [ 8.109399] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > >> [ 8.109614] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > >> [ 8.109836] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000101354000 > >> [ 8.110011] [0000000000000004] pgd=0000000000000000, p4d=0000000000000000 > >> [ 8.112624] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP > >> [ 8.112783] Modules linked in: > >> [ 8.113120] CPU: 0 PID: 99 Comm: may_access_dire Not tainted 6.10.0-rc3-next-20240613-dirty #1 > >> [ 8.113230] Hardware name: linux,dummy-virt (DT) > >> [ 8.113390] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > >> [ 8.113429] pc : may_access_direct_pkt_data+0x24/0xa0 > >> [ 8.113746] lr : add_subprog_and_kfunc+0x634/0x8e8 > >> [ 8.113798] sp : ffff80008283b9f0 > >> [ 8.113813] x29: ffff80008283b9f0 x28: ffff800082795048 x27: 0000000000000001 > >> [ 8.113881] x26: ffff0000c0bb2600 x25: 0000000000000000 x24: 0000000000000000 > >> [ 8.113897] x23: ffff0000c1134000 x22: 000000000001864f x21: ffff0000c1138000 > >> [ 8.113912] x20: 0000000000000001 x19: ffff0000c12b8000 x18: ffffffffffffffff > >> [ 8.113929] x17: 0000000000000000 x16: 0000000000000000 x15: 0720072007200720 > >> [ 8.113944] x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720 > >> [ 8.113958] x11: 0720072007200720 x10: 0000000000f9fca4 x9 : ffff80008021f4e4 > >> [ 8.113991] x8 : 0101010101010101 x7 : 746f72705f6d656d x6 : 000000001e0e0f5f > >> [ 8.114006] x5 : 000000000001864f x4 : ffff0000c12b8000 x3 : 000000000000001c > >> [ 8.114020] x2 : 0000000000000002 x1 : 0000000000000000 x0 : 0000000000000000 > >> [ 8.114126] Call trace: > >> [ 8.114159] may_access_direct_pkt_data+0x24/0xa0 > >> [ 8.114202] bpf_check+0x3bc/0x28c0 > >> [ 8.114214] bpf_prog_load+0x658/0xa58 > >> [ 8.114227] __sys_bpf+0xc50/0x2250 > >> [ 8.114240] __arm64_sys_bpf+0x28/0x40 > >> [ 8.114254] invoke_syscall.constprop.0+0x54/0xf0 > >> [ 8.114273] do_el0_svc+0x4c/0xd8 > >> [ 8.114289] el0_svc+0x3c/0x140 > >> [ 8.114305] el0t_64_sync_handler+0x134/0x150 > >> [ 8.114331] el0t_64_sync+0x168/0x170 > >> [ 8.114477] Code: 7100707f 54000081 f9401c00 f9403800 (b9400403) > >> [ 8.118672] ---[ end trace 0000000000000000 ]--- > >> > >> Fix this by adding dst_prog non-empty check in BPF_PROG_TYPE_EXT case > >> when calling bpf_prog_load(). > >> > >> Fixes: 4a9c7bbe2ed4 ("bpf: Resolve to prog->aux->dst_prog->type only for BPF_PROG_TYPE_EXT") > >> Signed-off-by: Tengda Wu > >> Cc: stable@vger.kernel.org # v5.18+ > >> --- > >> kernel/bpf/syscall.c | 5 ++++- > >> 1 file changed, 4 insertions(+), 1 deletion(-) > >> > >> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > >> index f45ed6adc092..4490f8ccf006 100644 > >> --- a/kernel/bpf/syscall.c > >> +++ b/kernel/bpf/syscall.c > >> @@ -2632,9 +2632,12 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, > >> return 0; > >> return -EINVAL; > >> case BPF_PROG_TYPE_SYSCALL: > >> - case BPF_PROG_TYPE_EXT: > >> if (expected_attach_type) > >> return -EINVAL; > >> + return 0; > >> + case BPF_PROG_TYPE_EXT: > >> + if (expected_attach_type || !dst_prog) > >> + return -EINVAL; > >> fallthrough; > >> default: > >> return 0; >