From patchwork Thu Jun 13 13:24:34 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arthur Fabre X-Patchwork-Id: 1115146 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=cloudflare.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=cloudflare.com header.i=@cloudflare.com header.b="keerC7ou"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45PnP53n7Jz9sPn for ; Fri, 14 Jun 2019 01:15:37 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733246AbfFMPPf (ORCPT ); Thu, 13 Jun 2019 11:15:35 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:46026 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732222AbfFMNZQ (ORCPT ); Thu, 13 Jun 2019 09:25:16 -0400 Received: by mail-wr1-f65.google.com with SMTP id f9so20747826wre.12 for ; Thu, 13 Jun 2019 06:25:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=H/XDzYueXffv1rUyJx1oEFA1jQkKQnEoAqI3KBmpQNQ=; b=keerC7oubO4xWDPqVdCuDXHlcwDp1ZGxBs6OtO0Jg9F0rB7opUoNZfaXAywrlZu5nM I+zPjctobOUMBWt7rFEArKp/IUuJNRdB1ulWSYXLeVdokX5WmkPYMWrbdMbkyTKUHevZ 7GdZskEhnLXcF6vcGs9LuGOSp+WrsAhmO4RsU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=H/XDzYueXffv1rUyJx1oEFA1jQkKQnEoAqI3KBmpQNQ=; b=oHffPCWkl8R0+GDqKxGyVEJeiL2r4uYt1fQ/5Yhdjo4UWLlAxCyzAhM9ePyEkpbenY cIroQVSDCClxfDI9MLh2FD+vPuFxo0RZN4P17MxnBNyzaxbyPNGOhlWrqE0Finj6oLHi 05D035qvEmq9gy3SLRpX3H3Hb8ejtb7S94a7wLo2buS4z9aZOsBZEjY2i/YMs2QwLgsH 4g1mOqlvJVnJpOGJEM5aScsM4TG9QBl+isrGcmt1u7E73eiLFbQHE+FpvREwMUuaTXrz 554G02dFunI5MIg56ZJDOQZRcEizlcx51PZGG2V1aIKWuEKfSvaGLvlDctFOwmNTSmON YIgA== X-Gm-Message-State: APjAAAVRwhN4P6sdiAel/kshd/rK2ZUfgPT8e2MsEdhiI3xL8WkwG/Yo Y6gWXbbK1KGy6/K/NCDG5naD7Q== X-Google-Smtp-Source: APXvYqwDEPlruy2eVqw9ZQATbv3Dsj0ZxtvE79jIaKuGvWhxiukBuyyX3IRiItW0qa3pl3HgnhuzQA== X-Received: by 2002:adf:c5c1:: with SMTP id v1mr41961383wrg.129.1560432313294; Thu, 13 Jun 2019 06:25:13 -0700 (PDT) Received: from localhost.localdomain ([147.12.216.9]) by smtp.gmail.com with ESMTPSA id d10sm3324109wrp.74.2019.06.13.06.25.12 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 13 Jun 2019 06:25:12 -0700 (PDT) From: Arthur Fabre To: "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Arthur Fabre Subject: [PATCH bpf-next] bpf: sk_storage: Fix out of bounds memory access Date: Thu, 13 Jun 2019 14:24:34 +0100 Message-Id: <20190613132433.17213-1-afabre@cloudflare.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org bpf_sk_storage maps use multiple spin locks to reduce contention. The number of locks to use is determined by the number of possible CPUs. With only 1 possible CPU, bucket_log == 0, and 2^0 = 1 locks are used. When updating elements, the correct lock is determined with hash_ptr(). Calling hash_ptr() with 0 bits is undefined behavior, as it does: x >> (64 - bits) Using the value results in an out of bounds memory access. In my case, this manifested itself as a page fault when raw_spin_lock_bh() is called later, when running the self tests: ./tools/testing/selftests/bpf/test_verifier 773 775 [ 16.366342] BUG: unable to handle page fault for address: ffff8fe7a66f93f8 [ 16.367139] #PF: supervisor write access in kernel mode [ 16.367751] #PF: error_code(0x0002) - not-present page [ 16.368323] PGD 35a01067 P4D 35a01067 PUD 0 [ 16.368796] Oops: 0002 [#1] SMP PTI [ 16.369175] CPU: 0 PID: 189 Comm: test_verifier Not tainted 5.2.0-rc2+ #10 [ 16.369960] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 [ 16.371021] RIP: 0010:_raw_spin_lock_bh (/home/afabre/linux/./include/trace/events/initcall.h:48) [ 16.371571] Code: 02 00 00 31 c0 ba ff 00 00 00 3e 0f b1 17 75 01 c3 e9 82 12 5f ff 66 90 65 81 05 ad 14 6f 41 00 02 00 00 31 c0 ba 01 00 00 00 <3e> 0f b1 17 75 01 c3 89 c6 e9 f0 02 5f ff b8 00 02 00 00 3e 0f c1 All code ======== 0: 02 00 add (%rax),%al 2: 00 31 add %dh,(%rcx) 4: c0 ba ff 00 00 00 3e sarb $0x3e,0xff(%rdx) b: 0f b1 17 cmpxchg %edx,(%rdi) e: 75 01 jne 0x11 10: c3 retq 11: e9 82 12 5f ff jmpq 0xffffffffff5f1298 16: 66 90 xchg %ax,%ax 18: 65 81 05 ad 14 6f 41 addl $0x200,%gs:0x416f14ad(%rip) # 0x416f14d0 1f: 00 02 00 00 23: 31 c0 xor %eax,%eax 25: ba 01 00 00 00 mov $0x1,%edx 2a: 3e 0f b1 17 cmpxchg %edx,%ds:*(%rdi) <-- trapping instruction 2e: 75 01 jne 0x31 30: c3 retq 31: 89 c6 mov %eax,%esi 33: e9 f0 02 5f ff jmpq 0xffffffffff5f0328 38: b8 00 02 00 00 mov $0x200,%eax 3d: 3e ds 3e: 0f .byte 0xf 3f: c1 .byte 0xc1 Code starting with the faulting instruction =========================================== 0: 3e 0f b1 17 cmpxchg %edx,%ds:(%rdi) 4: 75 01 jne 0x7 6: c3 retq 7: 89 c6 mov %eax,%esi 9: e9 f0 02 5f ff jmpq 0xffffffffff5f02fe e: b8 00 02 00 00 mov $0x200,%eax 13: 3e ds 14: 0f .byte 0xf 15: c1 .byte 0xc1 [ 16.373398] RSP: 0018:ffffa759809d3be0 EFLAGS: 00010246 [ 16.373954] RAX: 0000000000000000 RBX: ffff8fe7a66f93f0 RCX: 0000000000000040 [ 16.374645] RDX: 0000000000000001 RSI: ffff8fdaf9f0d180 RDI: ffff8fe7a66f93f8 [ 16.375338] RBP: ffff8fdaf9f0d180 R08: ffff8fdafba2c320 R09: ffff8fdaf9f0d0c0 [ 16.376028] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8fdafa346700 [ 16.376719] R13: ffff8fe7a66f93f8 R14: ffff8fdaf9f0d0c0 R15: 0000000000000001 [ 16.377413] FS: 00007fda724c0740(0000) GS:ffff8fdafba00000(0000) knlGS:0000000000000000 [ 16.378204] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 16.378763] CR2: ffff8fe7a66f93f8 CR3: 0000000139d1c006 CR4: 0000000000360ef0 [ 16.379453] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 16.380144] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 16.380864] Call Trace: [ 16.381112] selem_link_map (/home/afabre/linux/./include/linux/compiler.h:221 /home/afabre/linux/net/core/bpf_sk_storage.c:243) [ 16.381476] sk_storage_update (/home/afabre/linux/net/core/bpf_sk_storage.c:355 /home/afabre/linux/net/core/bpf_sk_storage.c:414) [ 16.381888] bpf_sk_storage_get (/home/afabre/linux/net/core/bpf_sk_storage.c:760 /home/afabre/linux/net/core/bpf_sk_storage.c:741) [ 16.382285] ___bpf_prog_run (/home/afabre/linux/kernel/bpf/core.c:1447) [ 16.382679] ? __bpf_prog_run32 (/home/afabre/linux/kernel/bpf/core.c:1603) [ 16.383074] ? alloc_file_pseudo (/home/afabre/linux/fs/file_table.c:232) [ 16.383486] ? kvm_clock_get_cycles (/home/afabre/linux/arch/x86/kernel/kvmclock.c:98) [ 16.383906] ? ktime_get (/home/afabre/linux/kernel/time/timekeeping.c:265 /home/afabre/linux/kernel/time/timekeeping.c:369 /home/afabre/linux/kernel/time/timekeeping.c:754) [ 16.384243] ? bpf_test_run (/home/afabre/linux/net/bpf/test_run.c:47) [ 16.384613] ? bpf_prog_test_run_skb (/home/afabre/linux/net/bpf/test_run.c:313) [ 16.385065] ? security_capable (/home/afabre/linux/security/security.c:696 (discriminator 19)) [ 16.385460] ? __do_sys_bpf (/home/afabre/linux/kernel/bpf/syscall.c:2072 /home/afabre/linux/kernel/bpf/syscall.c:2848) [ 16.385854] ? __handle_mm_fault (/home/afabre/linux/mm/memory.c:3507 /home/afabre/linux/mm/memory.c:3532 /home/afabre/linux/mm/memory.c:3666 /home/afabre/linux/mm/memory.c:3897 /home/afabre/linux/mm/memory.c:4021) [ 16.386273] ? __dentry_kill (/home/afabre/linux/fs/dcache.c:595) [ 16.386652] ? do_syscall_64 (/home/afabre/linux/arch/x86/entry/common.c:301) [ 16.387031] ? entry_SYSCALL_64_after_hwframe (/home/afabre/linux/./include/trace/events/initcall.h:10 /home/afabre/linux/./include/trace/events/initcall.h:10) [ 16.387541] Modules linked in: [ 16.387846] CR2: ffff8fe7a66f93f8 [ 16.388175] ---[ end trace 891cf27b5b9c9cc6 ]--- [ 16.388628] RIP: 0010:_raw_spin_lock_bh (/home/afabre/linux/./include/trace/events/initcall.h:48) [ 16.389089] Code: 02 00 00 31 c0 ba ff 00 00 00 3e 0f b1 17 75 01 c3 e9 82 12 5f ff 66 90 65 81 05 ad 14 6f 41 00 02 00 00 31 c0 ba 01 00 00 00 <3e> 0f b1 17 75 01 c3 89 c6 e9 f0 02 5f ff b8 00 02 00 00 3e 0f c1 All code ======== 0: 02 00 add (%rax),%al 2: 00 31 add %dh,(%rcx) 4: c0 ba ff 00 00 00 3e sarb $0x3e,0xff(%rdx) b: 0f b1 17 cmpxchg %edx,(%rdi) e: 75 01 jne 0x11 10: c3 retq 11: e9 82 12 5f ff jmpq 0xffffffffff5f1298 16: 66 90 xchg %ax,%ax 18: 65 81 05 ad 14 6f 41 addl $0x200,%gs:0x416f14ad(%rip) # 0x416f14d0 1f: 00 02 00 00 23: 31 c0 xor %eax,%eax 25: ba 01 00 00 00 mov $0x1,%edx 2a: 3e 0f b1 17 cmpxchg %edx,%ds:*(%rdi) <-- trapping instruction 2e: 75 01 jne 0x31 30: c3 retq 31: 89 c6 mov %eax,%esi 33: e9 f0 02 5f ff jmpq 0xffffffffff5f0328 38: b8 00 02 00 00 mov $0x200,%eax 3d: 3e ds 3e: 0f .byte 0xf 3f: c1 .byte 0xc1 Code starting with the faulting instruction =========================================== 0: 3e 0f b1 17 cmpxchg %edx,%ds:(%rdi) 4: 75 01 jne 0x7 6: c3 retq 7: 89 c6 mov %eax,%esi 9: e9 f0 02 5f ff jmpq 0xffffffffff5f02fe e: b8 00 02 00 00 mov $0x200,%eax 13: 3e ds 14: 0f .byte 0xf 15: c1 .byte 0xc1 [ 16.390899] RSP: 0018:ffffa759809d3be0 EFLAGS: 00010246 [ 16.391410] RAX: 0000000000000000 RBX: ffff8fe7a66f93f0 RCX: 0000000000000040 [ 16.392102] RDX: 0000000000000001 RSI: ffff8fdaf9f0d180 RDI: ffff8fe7a66f93f8 [ 16.392795] RBP: ffff8fdaf9f0d180 R08: ffff8fdafba2c320 R09: ffff8fdaf9f0d0c0 [ 16.393481] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8fdafa346700 [ 16.394169] R13: ffff8fe7a66f93f8 R14: ffff8fdaf9f0d0c0 R15: 0000000000000001 [ 16.394870] FS: 00007fda724c0740(0000) GS:ffff8fdafba00000(0000) knlGS:0000000000000000 [ 16.395641] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 16.396193] CR2: ffff8fe7a66f93f8 CR3: 0000000139d1c006 CR4: 0000000000360ef0 [ 16.396876] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 16.397557] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 16.398246] Kernel panic - not syncing: Fatal exception in interrupt [ 16.399067] Kernel Offset: 0x3ce00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 16.400098] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]--- Signed-off-by: Arthur Fabre Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage") --- net/core/bpf_sk_storage.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index f40e3d35fd9c..7ae0686c5418 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -90,7 +90,13 @@ struct bpf_sk_storage { static struct bucket *select_bucket(struct bpf_sk_storage_map *smap, struct bpf_sk_storage_elem *selem) { - return &smap->buckets[hash_ptr(selem, smap->bucket_log)]; + /* hash_ptr is undefined behavior with 0 bits */ + int bucket = 0; + if (smap->bucket_log != 0) { + bucket = hash_ptr(selem, smap->bucket_log); + } + + return &smap->buckets[bucket]; } static int omem_charge(struct sock *sk, unsigned int size)