From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FBE4C31E4E for ; Fri, 14 Jun 2019 22:32:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 63FD020866 for ; Fri, 14 Jun 2019 22:32:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ikN9b9uD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726185AbfFNWcE (ORCPT ); Fri, 14 Jun 2019 18:32:04 -0400 Received: from mail-qk1-f195.google.com ([209.85.222.195]:39848 "EHLO mail-qk1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725812AbfFNWcE (ORCPT ); Fri, 14 Jun 2019 18:32:04 -0400 Received: by mail-qk1-f195.google.com with SMTP id i125so2713891qkd.6; Fri, 14 Jun 2019 15:32:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=rgCpxQhKgcPxKhW1zrmoJ7xR10La2/Y/NCUBA1QHYKg=; b=ikN9b9uDtTN2fuFFRirNtEKSGBtekPBwAtjcFoeDYo/n4GIpdxNrzEGxoDEveSyn8q RvkLP2zVpnhR+bG0cWFd7Tb6iIth3zBxO+iwVI2/QLxamk1wZu7clV00s0UkOQUCz/Fb j3PChAdTCsFcY9tPY8KCPwsoJI7wVqN3kuzQSMxjrHDJTI69ORMqUq9bnvspSjB24Zz1 9rCTA/XbPCIIAQ97NmBee5gYHRCHzhfxx/tA2HAk3+2y9F9HVBnMvXzOg/AldoUDnKBA rElPQB/qGT9+XRCAOzJ1+8nqVrO93GSbS0YOViSaszr12PN4+VRaObPuTAL6wKcBOn8P AITg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rgCpxQhKgcPxKhW1zrmoJ7xR10La2/Y/NCUBA1QHYKg=; b=Jruzngf9Oa7Mpu5e83gMr+wd2rYWiOKg5mbB50oDHLV0sXzdCQsqJQhTu/VsHzQIiA u5/Ne3J0844X/NUOePWpYlEh2RFakrnny/8FlXJIEVa7r0jENeLmepE5iRQdj9FryUN0 XW5l3c8b5+Af9d+hmcnC5604CYfhd1TAnIg7Ktzry6iQIhCY5iOCEE9Vd0Vhf+dUNvIq YtgVLiicGFyhs4BgGFIAs8tyDK46a5qA/g28dhHjpKFJbLP+zmVky3T1XHRmW8LMqhae A+GgmY9HyM5y4Pc/C3Vy7Kd8gi76khQpbRsakmoPXNsCg6VYKgga3FiJorH3nMZLH64j u6QA== X-Gm-Message-State: APjAAAWv4R/19XfQANNkdsdEARzn6Q9upR74GVovdggBYuEsGA34/onf 1dtVfpctSKFbuz/FQPDZiXVS7awBS0lnmMi6mr4= X-Google-Smtp-Source: APXvYqxRdVKeHpuHoTUPPVHtYPrH6D+wdvvqXiopjY5+9iDYXwZhVjB0bYX6Tkeyh1IghaRBHtdk0PKTOp+7Id11Ct0= X-Received: by 2002:ae9:eb53:: with SMTP id b80mr49509306qkg.172.1560551522210; Fri, 14 Jun 2019 15:32:02 -0700 (PDT) MIME-Version: 1.0 References: <20190614093728.622-1-afabre@cloudflare.com> In-Reply-To: <20190614093728.622-1-afabre@cloudflare.com> From: Andrii Nakryiko Date: Fri, 14 Jun 2019 15:31:51 -0700 Message-ID: Subject: Re: [PATCH v2 bpf-next] bpf: sk_storage: Fix out of bounds memory access To: Arthur Fabre Cc: "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Networking , bpf , open list Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jun 14, 2019 at 2:45 AM Arthur Fabre wrote: > > 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 ]--- > I think the bug is pretty clear without this detailed example, I'd remove it from commit message. > Force the minimum number of locks to two. > > Signed-off-by: Arthur Fabre > Fixes: 6ac99e8f23d4 ("bpf: Introduce bpf sk local storage") > --- Thanks for fixing this! Acked-by: Andrii Nakryiko > net/core/bpf_sk_storage.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c > index f40e3d35fd9c..94c7f77ecb6b 100644 > --- a/net/core/bpf_sk_storage.c > +++ b/net/core/bpf_sk_storage.c > @@ -634,7 +634,8 @@ static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr) > return ERR_PTR(-ENOMEM); > bpf_map_init_from_attr(&smap->map, attr); > > - smap->bucket_log = ilog2(roundup_pow_of_two(num_possible_cpus())); > + /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */ > + smap->bucket_log = max_t(u32, 1, ilog2(roundup_pow_of_two(num_possible_cpus()))); > nbuckets = 1U << smap->bucket_log; > cost = sizeof(*smap->buckets) * nbuckets + sizeof(*smap); > > -- > 2.20.1 >