From patchwork Sat Oct 7 07:51:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Kanner X-Patchwork-Id: 13412226 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 7DEC88481; Sat, 7 Oct 2023 07:52:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="joZKHjJg" Received: from mail-ed1-x52d.google.com (mail-ed1-x52d.google.com [IPv6:2a00:1450:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B19E7A6; Sat, 7 Oct 2023 00:52:50 -0700 (PDT) Received: by mail-ed1-x52d.google.com with SMTP id 4fb4d7f45d1cf-533d31a8523so5294767a12.1; Sat, 07 Oct 2023 00:52:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1696665169; x=1697269969; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=FYYo8GR3oiE1tO7of8Zj0AJ+1K2a6alvRcy0hRc5+D0=; b=joZKHjJgRJLEAaiqi+g/61Q7wUZkNDC2rPdP/J/g/++zZHTqARZg7CVziDrMEb9NqU 2yuHRlJ/aGB6zaZWhmOJMGpJ6lRub6OfNcPgA/tG2znMn3j7AdyDcY7PcNuI6Fqtrne/ BM67BLYO8bM/CuqxPHVrptm2eBM9BAadnjHtKbQ9+9caDcb6x84H00+o+f1WQAMxVpnI SpHB3s6nZmfk3I4ojSQ8FLIKsT+WHzWHtrMXFbsjrdgCsPLgagfP6nl+T/JFHOtvPP6U 8nMV7TnPzXN9rrZF9CSsO0NGA4qUSzU1HI4cWK7vcdP3gLtxEBPK/g7L4qRIZohiFgzz gn3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696665169; x=1697269969; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=FYYo8GR3oiE1tO7of8Zj0AJ+1K2a6alvRcy0hRc5+D0=; b=n2Uy5Tk4ZdpV73L788JGaMXLM5Xehf+oScGNjLVMRhyMNB6voviiQoYPmLk9HuJEIN vlnyQJRZaJoSBEr0pD7sEFNFmvAKBJLdCt4BZt8EyTe1HEonzNDAKAswTrHIMgW0Wkbc dB9SwdwpUwsBmzfrhRox3L7yKD2qb9XY9ZiT4UEz1DX86Wp9yHjaeqH5f6A2I2Ok9208 03OEBT2SAWKifkf2RuhMczyqAgYtWclGvx3B9AQZLclFypWLHprFl0C8tJYLabJrxmqK 2JBMGAWLR2jCnT+DhOd5Y3uBrOlJabuwy0xX/YCjXGXrlfTAHtHMjvFNtl152/0TG42Y nVfA== X-Gm-Message-State: AOJu0YxvosBpb/O+3Z1o3/T/8Q8brmCFDF0Q28FUrqYhbZL6gteo33jG tj3FN91Ue2IZQFJyxtK/AZweP8XCFmDFQw== X-Google-Smtp-Source: AGHT+IEa0d+g1RmX9uc9gMWr0k5mS4QILCecL+NREQqJlgOannZCmyfEkeEcOEKCxv16TAPphXhn1Q== X-Received: by 2002:a50:ee1a:0:b0:530:a0a9:ee36 with SMTP id g26-20020a50ee1a000000b00530a0a9ee36mr8902769eds.38.1696665168939; Sat, 07 Oct 2023 00:52:48 -0700 (PDT) Received: from localhost.localdomain ([77.222.24.57]) by smtp.gmail.com with ESMTPSA id n24-20020aa7d058000000b0053331f9094dsm3568685edo.52.2023.10.07.00.52.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Oct 2023 00:52:44 -0700 (PDT) From: Andrew Kanner To: martin.lau@linux.dev, bjorn@kernel.org, magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, aleksander.lobakin@intel.com, xuanzhuo@linux.alibaba.com, ast@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, daniel@iogearbox.net Cc: linux-kernel-mentees@lists.linuxfoundation.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+fae676d3cf469331fc89@syzkaller.appspotmail.com, syzbot+b132693e925cbbd89e26@syzkaller.appspotmail.com, Andrew Kanner Subject: [PATCH bpf v4] net/xdp: fix zero-size allocation warning in xskq_create() Date: Sat, 7 Oct 2023 10:51:49 +0300 Message-Id: <20231007075148.1759-1-andrew.kanner@gmail.com> X-Mailer: git-send-email 2.39.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net Syzkaller reported the following issue: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 2807 at mm/vmalloc.c:3247 __vmalloc_node_range (mm/vmalloc.c:3361) Modules linked in: CPU: 0 PID: 2807 Comm: repro Not tainted 6.6.0-rc2+ #12 Hardware name: Generic DT based system unwind_backtrace from show_stack (arch/arm/kernel/traps.c:258) show_stack from dump_stack_lvl (lib/dump_stack.c:107 (discriminator 1)) dump_stack_lvl from __warn (kernel/panic.c:633 kernel/panic.c:680) __warn from warn_slowpath_fmt (./include/linux/context_tracking.h:153 kernel/panic.c:700) warn_slowpath_fmt from __vmalloc_node_range (mm/vmalloc.c:3361 (discriminator 3)) __vmalloc_node_range from vmalloc_user (mm/vmalloc.c:3478) vmalloc_user from xskq_create (net/xdp/xsk_queue.c:40) xskq_create from xsk_setsockopt (net/xdp/xsk.c:953 net/xdp/xsk.c:1286) xsk_setsockopt from __sys_setsockopt (net/socket.c:2308) __sys_setsockopt from ret_fast_syscall (arch/arm/kernel/entry-common.S:68) xskq_get_ring_size() uses struct_size() macro to safely calculate the size of struct xsk_queue and q->nentries of desc members. But the syzkaller repro was able to set q->nentries with the value initially taken from copy_from_sockptr() high enough to return SIZE_MAX by struct_size(). The next PAGE_ALIGN(size) is such case will overflow the size_t value and set it to 0. This will trigger WARN_ON_ONCE in vmalloc_user() -> __vmalloc_node_range(). The issue is reproducible on 32-bit arm kernel. Reported-and-tested-by: syzbot+fae676d3cf469331fc89@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000c84b4705fb31741e@google.com/T/ Link: https://syzkaller.appspot.com/bug?extid=fae676d3cf469331fc89 Reported-by: syzbot+b132693e925cbbd89e26@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000e20df20606ebab4f@google.com/T/ Fixes: 9f78bf330a66 ("xsk: support use vaddr as ring") Signed-off-by: Andrew Kanner Acked-by: Magnus Karlsson --- Notes (akanner): v4: - add explanation about SIZE_MAX, suggested by Martin KaFai Lau v3: https://lore.kernel.org/all/20231005193548.515-1-andrew.kanner@gmail.com/T/ - free kzalloc-ed memory before return, the leak was noticed by Daniel Borkmann v2: https://lore.kernel.org/all/20231002222939.1519-1-andrew.kanner@gmail.com/raw - use unlikely() optimization for the case with SIZE_MAX return from struct_size(), suggested by Alexander Lobakin - cc-ed 4 more maintainers, mentioned by cc_maintainers patchwork test v1: https://lore.kernel.org/all/20230928204440.543-1-andrew.kanner@gmail.com/T/ - RFC notes: It was found that net/xdp/xsk.c:xsk_setsockopt() uses copy_from_sockptr() to get the number of entries (int) for cases with XDP_RX_RING / XDP_TX_RING and XDP_UMEM_FILL_RING / XDP_UMEM_COMPLETION_RING. Next in xsk_init_queue() there're 2 sanity checks (entries == 0) and (!is_power_of_2(entries)) for which -EINVAL will be returned. After that net/xdp/xsk_queue.c:xskq_create() will calculate the size multipling the number of entries (int) with the size of u64, at least. I wonder if there should be the upper bound (e.g. the 3rd sanity check inside xsk_init_queue()). It seems that without the upper limit it's quiet easy to overflow the allocated size (SIZE_MAX), especially for 32-bit architectures, for example arm nodes which were used by the syzkaller. In this patch I added a naive check for SIZE_MAX which helped to skip zero-size allocation after overflow, but maybe it's not quite right. Please, suggest if you have any thoughts about the appropriate limit for the size of these xdp rings. PS: the initial number of entries is 0x20000000 in syzkaller repro: syscall(__NR_setsockopt, (intptr_t)r[0], 0x11b, 3, 0x20000040, 0x20); Link: https://syzkaller.appspot.com/text?tag=ReproC&x=10910f18280000 net/xdp/xsk_queue.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/net/xdp/xsk_queue.c b/net/xdp/xsk_queue.c index f8905400ee07..d2c264030017 100644 --- a/net/xdp/xsk_queue.c +++ b/net/xdp/xsk_queue.c @@ -34,6 +34,16 @@ struct xsk_queue *xskq_create(u32 nentries, bool umem_queue) q->ring_mask = nentries - 1; size = xskq_get_ring_size(q, umem_queue); + + /* size which is overflowing or close to SIZE_MAX will become 0 in + * PAGE_ALIGN(), checking SIZE_MAX is enough due to the previous + * is_power_of_2(), the rest will be handled by vmalloc_user() + */ + if (unlikely(size == SIZE_MAX)) { + kfree(q); + return NULL; + } + size = PAGE_ALIGN(size); q->ring = vmalloc_user(size);