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[84.238.136.197]) by smtp.gmail.com with ESMTPSA id o20sm3626926lfg.45.2020.02.24.00.51.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2020 00:51:03 -0800 (PST) Subject: Re: KMSAN: uninit-value in br_dev_xmit To: syzbot , bridge@lists.linux-foundation.org, davem@davemloft.net, glider@google.com, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, roopa@cumulusnetworks.com, syzkaller-bugs@googlegroups.com References: <000000000000c0910e059f4e4a82@google.com> From: Nikolay Aleksandrov Message-ID: <08a2e28b-fcf5-b26c-da75-97df67f51c7c@cumulusnetworks.com> Date: Mon, 24 Feb 2020 10:51:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <000000000000c0910e059f4e4a82@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/02/2020 10:38, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 8bbbc5cf kmsan: don't compile memmove > git tree: https://github.com/google/kmsan.git master > console output: https://syzkaller.appspot.com/x/log.txt?x=14d9a3d9e00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=cd0e9a6b0e555cc3 > dashboard link: https://syzkaller.appspot.com/bug?extid=18c8b623c66fc198c493 > compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) > userspace arch: i386 > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+18c8b623c66fc198c493@syzkaller.appspotmail.com > br_allowed_ingress() can call skb_vlan_untag() which does pskb_may_pull() and so the cached eth header can become invalid. I'll prepare a fix. Cheers, Nik > ===================================================== > BUG: KMSAN: uninit-value in br_dev_xmit+0x99a/0x1730 net/bridge/br_device.c:64 > CPU: 0 PID: 14704 Comm: syz-executor.1 Not tainted 5.6.0-rc2-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x1c9/0x220 lib/dump_stack.c:118 > kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118 > __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 > br_dev_xmit+0x99a/0x1730 net/bridge/br_device.c:64 > __netdev_start_xmit include/linux/netdevice.h:4524 [inline] > netdev_start_xmit include/linux/netdevice.h:4538 [inline] > xmit_one net/core/dev.c:3470 [inline] > dev_hard_start_xmit+0x531/0xab0 net/core/dev.c:3486 > __dev_queue_xmit+0x37de/0x4220 net/core/dev.c:4063 > dev_queue_xmit+0x4b/0x60 net/core/dev.c:4096 > __bpf_tx_skb net/core/filter.c:2061 [inline] > __bpf_redirect_common net/core/filter.c:2100 [inline] > __bpf_redirect+0x11d5/0x1440 net/core/filter.c:2107 > ____bpf_clone_redirect net/core/filter.c:2140 [inline] > bpf_clone_redirect+0x466/0x620 net/core/filter.c:2112 > bpf_prog_a481c1313990ee2c+0x5e0/0x1000 > bpf_dispatcher_nopfunc include/linux/bpf.h:521 [inline] > bpf_test_run+0x60c/0xe50 net/bpf/test_run.c:48 > bpf_prog_test_run_skb+0xcab/0x24a0 net/bpf/test_run.c:388 > bpf_prog_test_run kernel/bpf/syscall.c:2572 [inline] > __do_sys_bpf+0xa684/0x13510 kernel/bpf/syscall.c:3414 > __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] > __ia32_sys_bpf+0xdb/0x120 kernel/bpf/syscall.c:3355 > do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline] > do_fast_syscall_32+0x3c7/0x6e0 arch/x86/entry/common.c:410 > entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139 > RIP: 0023:0xf7f79d99 > Code: 90 e8 0b 00 00 00 f3 90 0f ae e8 eb f9 8d 74 26 00 89 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 > RSP: 002b:00000000f5d740cc EFLAGS: 00000296 ORIG_RAX: 0000000000000165 > RAX: ffffffffffffffda RBX: 000000000000000a RCX: 0000000020000140 > RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > > Uninit was created at: > kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline] > kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127 > kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:82 > slab_alloc_node mm/slub.c:2793 [inline] > __kmalloc_node_track_caller+0xb40/0x1200 mm/slub.c:4401 > __kmalloc_reserve net/core/skbuff.c:142 [inline] > pskb_expand_head+0x20b/0x1b00 net/core/skbuff.c:1629 > skb_ensure_writable+0x3ea/0x490 net/core/skbuff.c:5453 > __bpf_try_make_writable net/core/filter.c:1635 [inline] > bpf_try_make_writable net/core/filter.c:1641 [inline] > bpf_try_make_head_writable net/core/filter.c:1649 [inline] > ____bpf_clone_redirect net/core/filter.c:2134 [inline] > bpf_clone_redirect+0x251/0x620 net/core/filter.c:2112 > bpf_prog_a481c1313990ee2c+0x5e0/0x1000 > bpf_dispatcher_nopfunc include/linux/bpf.h:521 [inline] > bpf_test_run+0x60c/0xe50 net/bpf/test_run.c:48 > bpf_prog_test_run_skb+0xcab/0x24a0 net/bpf/test_run.c:388 > bpf_prog_test_run kernel/bpf/syscall.c:2572 [inline] > __do_sys_bpf+0xa684/0x13510 kernel/bpf/syscall.c:3414 > __se_sys_bpf kernel/bpf/syscall.c:3355 [inline] > __ia32_sys_bpf+0xdb/0x120 kernel/bpf/syscall.c:3355 > do_syscall_32_irqs_on arch/x86/entry/common.c:339 [inline] > do_fast_syscall_32+0x3c7/0x6e0 arch/x86/entry/common.c:410 > entry_SYSENTER_compat+0x68/0x77 arch/x86/entry/entry_64_compat.S:139 > ===================================================== > > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. >