* [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb @ 2021-05-17 11:27 syzbot 2021-05-17 14:05 ` Willem de Bruijn 0 siblings, 1 reply; 7+ messages in thread From: syzbot @ 2021-05-17 11:27 UTC (permalink / raw) To: andrii, ast, bpf, daniel, davem, glider, john.fastabend, kafai, kpsingh, kuba, linux-kernel, netdev, songliubraving, syzkaller-bugs, tannerlove, willemb, xie.he.0141, yhs Hello, syzbot found the following issue on: HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. git tree: https://github.com/google/kmsan.git master console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 compiler: Debian clang version 11.0.1-2 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com ===================================================== BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 packet_snd net/packet/af_packet.c:2994 [inline] packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 kernel_sendpage+0x47a/0x590 net/socket.c:3631 sock_sendpage+0x161/0x1a0 net/socket.c:947 pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 splice_from_pipe_feed fs/splice.c:418 [inline] __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 splice_from_pipe fs/splice.c:597 [inline] generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 do_splice_from fs/splice.c:767 [inline] do_splice+0x23c3/0x2c10 fs/splice.c:1079 __do_splice fs/splice.c:1144 [inline] __do_sys_splice fs/splice.c:1350 [inline] __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x449a39 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 Uninit was created at: kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 alloc_pages include/linux/gfp.h:561 [inline] alloc_slab_page mm/slub.c:1653 [inline] allocate_slab+0x364/0x1260 mm/slub.c:1793 new_slab mm/slub.c:1856 [inline] new_slab_objects mm/slub.c:2602 [inline] ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 __slab_alloc mm/slub.c:2805 [inline] slab_alloc_node mm/slub.c:2886 [inline] slab_alloc mm/slub.c:2931 [inline] kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 kmalloc include/linux/slab.h:554 [inline] kzalloc include/linux/slab.h:684 [inline] ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 __ip_mc_inc_group net/ipv4/igmp.c:1470 [inline] ip_mc_inc_group net/ipv4/igmp.c:1476 [inline] ip_mc_up+0x1ec/0x410 net/ipv4/igmp.c:1775 inetdev_event+0x2036/0x20e0 net/ipv4/devinet.c:1573 notifier_call_chain kernel/notifier.c:83 [inline] raw_notifier_call_chain+0x123/0x290 kernel/notifier.c:410 __dev_notify_flags+0x5ac/0xba0 net/core/dev.c:2075 dev_change_flags+0x1f8/0x280 net/core/dev.c:8762 do_setlink+0x17f6/0x7890 net/core/rtnetlink.c:2708 __rtnl_newlink net/core/rtnetlink.c:3376 [inline] rtnl_newlink+0x2fc4/0x3d80 net/core/rtnetlink.c:3491 rtnetlink_rcv_msg+0x143b/0x18e0 net/core/rtnetlink.c:5553 netlink_rcv_skb+0x6fa/0x810 net/netlink/af_netlink.c:2502 rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5571 netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline] netlink_unicast+0x11d6/0x14a0 net/netlink/af_netlink.c:1338 netlink_sendmsg+0x1740/0x1840 net/netlink/af_netlink.c:1927 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] __sys_sendto+0x9ea/0xc60 net/socket.c:1977 __do_sys_sendto net/socket.c:1989 [inline] __se_sys_sendto+0x107/0x130 net/socket.c:1985 __x64_sys_sendto+0x6e/0x90 net/socket.c:1985 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 entry_SYSCALL_64_after_hwframe+0x44/0xae ===================================================== --- This report 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 issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb 2021-05-17 11:27 [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb syzbot @ 2021-05-17 14:05 ` Willem de Bruijn 2021-05-17 14:21 ` Dmitry Vyukov 0 siblings, 1 reply; 7+ messages in thread From: Willem de Bruijn @ 2021-05-17 14:05 UTC (permalink / raw) To: syzbot Cc: Andrii Nakryiko, Alexei Starovoitov, bpf, Daniel Borkmann, David Miller, Alexander Potapenko, John Fastabend, Martin Lau, KP Singh, Jakub Kicinski, linux-kernel, Network Development, Song Liu, syzkaller-bugs, Tanner Love, Xie He, Yonghong Song On Mon, May 17, 2021 at 7:27 AM syzbot <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. > git tree: https://github.com/google/kmsan.git master > console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 > dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 > compiler: Debian clang version 11.0.1-2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com > > ===================================================== > BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 No answer/fix, just initial investigation. This is an odd location. Line 86 is the inner if statement. Both protocol and skb->protocol are clearly initialized by then. But, that is also not the allocation that MSAN reports, see below. if (!skb->protocol) { __be16 protocol = dev_parse_header_protocol(skb); virtio_net_hdr_set_proto(skb, hdr); if (protocol && protocol != skb->protocol) return -EINVAL; } The repro itself seems mostly straightforward: - create a packet socket - enable PACKET_VNET_HDR with setsockopt(r3, 0x107, 0xf ..) - bind to AF_PACKET (0x11) - create a pipe - write to pipe[1] - splice pipe[0] to the packet socket there are a few other calls that I think are irrelevant and/or would fail. Perhaps there is some race condition in device refcounting, as bind operates on that? > CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:79 [inline] > dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 > virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > packet_snd net/packet/af_packet.c:2994 [inline] > packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 > sock_sendmsg_nosec net/socket.c:654 [inline] > sock_sendmsg net/socket.c:674 [inline] > kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 > sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 > kernel_sendpage+0x47a/0x590 net/socket.c:3631 > sock_sendpage+0x161/0x1a0 net/socket.c:947 > pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 > splice_from_pipe_feed fs/splice.c:418 [inline] > __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 > splice_from_pipe fs/splice.c:597 [inline] > generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 > do_splice_from fs/splice.c:767 [inline] > do_splice+0x23c3/0x2c10 fs/splice.c:1079 > __do_splice fs/splice.c:1144 [inline] > __do_sys_splice fs/splice.c:1350 [inline] > __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 > __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 > do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x449a39 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 > RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 > RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 > RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c > R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 > > Uninit was created at: > kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 > kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 > __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 > alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 > alloc_pages include/linux/gfp.h:561 [inline] > alloc_slab_page mm/slub.c:1653 [inline] > allocate_slab+0x364/0x1260 mm/slub.c:1793 > new_slab mm/slub.c:1856 [inline] > new_slab_objects mm/slub.c:2602 [inline] > ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 > __slab_alloc mm/slub.c:2805 [inline] > slab_alloc_node mm/slub.c:2886 [inline] > slab_alloc mm/slub.c:2931 [inline] > kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 > kmalloc include/linux/slab.h:554 [inline] > kzalloc include/linux/slab.h:684 [inline] > ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 This allocates ip_mc_list, but it uses kzalloc. Can that ever count as uninitialized? ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb 2021-05-17 14:05 ` Willem de Bruijn @ 2021-05-17 14:21 ` Dmitry Vyukov 2021-05-17 15:13 ` Willem de Bruijn 0 siblings, 1 reply; 7+ messages in thread From: Dmitry Vyukov @ 2021-05-17 14:21 UTC (permalink / raw) To: Willem de Bruijn Cc: syzbot, Andrii Nakryiko, Alexei Starovoitov, bpf, Daniel Borkmann, David Miller, Alexander Potapenko, John Fastabend, Martin Lau, KP Singh, Jakub Kicinski, linux-kernel, Network Development, Song Liu, syzkaller-bugs, Tanner Love, Xie He, Yonghong Song On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote: > > On Mon, May 17, 2021 at 7:27 AM syzbot > <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. > > git tree: https://github.com/google/kmsan.git master > > console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 > > dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 > > compiler: Debian clang version 11.0.1-2 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com > > > > ===================================================== > > BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > > No answer/fix, just initial investigation. > > This is an odd location. Line 86 is the inner if statement. Both > protocol and skb->protocol are clearly initialized by then. But, that > is also not the allocation that MSAN reports, see below. > > if (!skb->protocol) { > __be16 protocol = > dev_parse_header_protocol(skb); > > virtio_net_hdr_set_proto(skb, hdr); > if (protocol && protocol != skb->protocol) > return -EINVAL; > } > > The repro itself seems mostly straightforward: > > - create a packet socket > - enable PACKET_VNET_HDR with setsockopt(r3, 0x107, 0xf ..) > - bind to AF_PACKET (0x11) > > - create a pipe > - write to pipe[1] > - splice pipe[0] to the packet socket > > there are a few other calls that I think are irrelevant and/or would fail. > > Perhaps there is some race condition in device refcounting, as bind > operates on that? > > > CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:79 [inline] > > dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 > > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > > __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 > > virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > > packet_snd net/packet/af_packet.c:2994 [inline] > > packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 > > sock_sendmsg_nosec net/socket.c:654 [inline] > > sock_sendmsg net/socket.c:674 [inline] > > kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 > > sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 > > kernel_sendpage+0x47a/0x590 net/socket.c:3631 > > sock_sendpage+0x161/0x1a0 net/socket.c:947 > > pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 > > splice_from_pipe_feed fs/splice.c:418 [inline] > > __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 > > splice_from_pipe fs/splice.c:597 [inline] > > generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 > > do_splice_from fs/splice.c:767 [inline] > > do_splice+0x23c3/0x2c10 fs/splice.c:1079 > > __do_splice fs/splice.c:1144 [inline] > > __do_sys_splice fs/splice.c:1350 [inline] > > __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 > > __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 > > do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > RIP: 0033:0x449a39 > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > > RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 > > RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 > > RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 > > RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c > > R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 > > > > Uninit was created at: > > kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 > > kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 > > __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 > > alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 > > alloc_pages include/linux/gfp.h:561 [inline] > > alloc_slab_page mm/slub.c:1653 [inline] > > allocate_slab+0x364/0x1260 mm/slub.c:1793 > > new_slab mm/slub.c:1856 [inline] > > new_slab_objects mm/slub.c:2602 [inline] > > ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 > > __slab_alloc mm/slub.c:2805 [inline] > > slab_alloc_node mm/slub.c:2886 [inline] > > slab_alloc mm/slub.c:2931 [inline] > > kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 > > kmalloc include/linux/slab.h:554 [inline] > > kzalloc include/linux/slab.h:684 [inline] > > ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 > > This allocates ip_mc_list, but it uses kzalloc. Can that ever count as > uninitialized? Yes, kzalloc should never be a source of uninitialized-ness. But it's not actually this kzalloc, it's underlying page allocation (that is allocated uninitialized, so can be source of uninitialized-ness). If it would be this kzalloc, then stack would be shorter, along the lines of kzalloc->kmem_cache_alloc_trace->kmsan_save_stack_with_flags. This smells like a wild access in virtio_net_hdr_to_skb, which just hit a random uninit somewhere. Searching for virtio_net_hdr_to_skb I found this: KASAN: use-after-free Read in eth_header_parse_protocol https://syzkaller.appspot.com/bug?id=a486048b63065fd224f57b16d5a2fdece2b40eca Can it be a dup of that bug? ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb 2021-05-17 14:21 ` Dmitry Vyukov @ 2021-05-17 15:13 ` Willem de Bruijn 2021-05-17 15:44 ` Dmitry Vyukov 0 siblings, 1 reply; 7+ messages in thread From: Willem de Bruijn @ 2021-05-17 15:13 UTC (permalink / raw) To: Dmitry Vyukov Cc: syzbot, Andrii Nakryiko, Alexei Starovoitov, bpf, Daniel Borkmann, David Miller, Alexander Potapenko, John Fastabend, Martin Lau, KP Singh, Jakub Kicinski, linux-kernel, Network Development, Song Liu, syzkaller-bugs, Tanner Love, Xie He, Yonghong Song On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <dvyukov@google.com> wrote: > > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn > <willemdebruijn.kernel@gmail.com> wrote: > > > > On Mon, May 17, 2021 at 7:27 AM syzbot > > <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: > > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. > > > git tree: https://github.com/google/kmsan.git master > > > console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 > > > compiler: Debian clang version 11.0.1-2 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com > > > > > > ===================================================== > > > BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > > > > No answer/fix, just initial investigation. > > > > This is an odd location. Line 86 is the inner if statement. Both > > protocol and skb->protocol are clearly initialized by then. But, that > > is also not the allocation that MSAN reports, see below. > > > > if (!skb->protocol) { > > __be16 protocol = > > dev_parse_header_protocol(skb); > > > > virtio_net_hdr_set_proto(skb, hdr); > > if (protocol && protocol != skb->protocol) > > return -EINVAL; > > } > > > > The repro itself seems mostly straightforward: > > > > - create a packet socket > > - enable PACKET_VNET_HDR with setsockopt(r3, 0x107, 0xf ..) > > - bind to AF_PACKET (0x11) > > > > - create a pipe > > - write to pipe[1] > > - splice pipe[0] to the packet socket > > > > there are a few other calls that I think are irrelevant and/or would fail. > > > > Perhaps there is some race condition in device refcounting, as bind > > operates on that? > > > > > CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > Call Trace: > > > __dump_stack lib/dump_stack.c:79 [inline] > > > dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 > > > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > > > __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 > > > virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > > > packet_snd net/packet/af_packet.c:2994 [inline] > > > packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 > > > sock_sendmsg_nosec net/socket.c:654 [inline] > > > sock_sendmsg net/socket.c:674 [inline] > > > kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 > > > sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 > > > kernel_sendpage+0x47a/0x590 net/socket.c:3631 > > > sock_sendpage+0x161/0x1a0 net/socket.c:947 > > > pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 > > > splice_from_pipe_feed fs/splice.c:418 [inline] > > > __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 > > > splice_from_pipe fs/splice.c:597 [inline] > > > generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 > > > do_splice_from fs/splice.c:767 [inline] > > > do_splice+0x23c3/0x2c10 fs/splice.c:1079 > > > __do_splice fs/splice.c:1144 [inline] > > > __do_sys_splice fs/splice.c:1350 [inline] > > > __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 > > > __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 > > > do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > RIP: 0033:0x449a39 > > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > > > RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 > > > RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 > > > RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 > > > RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 > > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c > > > R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 > > > > > > Uninit was created at: > > > kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 > > > kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 > > > __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 > > > alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 > > > alloc_pages include/linux/gfp.h:561 [inline] > > > alloc_slab_page mm/slub.c:1653 [inline] > > > allocate_slab+0x364/0x1260 mm/slub.c:1793 > > > new_slab mm/slub.c:1856 [inline] > > > new_slab_objects mm/slub.c:2602 [inline] > > > ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 > > > __slab_alloc mm/slub.c:2805 [inline] > > > slab_alloc_node mm/slub.c:2886 [inline] > > > slab_alloc mm/slub.c:2931 [inline] > > > kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 > > > kmalloc include/linux/slab.h:554 [inline] > > > kzalloc include/linux/slab.h:684 [inline] > > > ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 > > > > This allocates ip_mc_list, but it uses kzalloc. Can that ever count as > > uninitialized? > > Yes, kzalloc should never be a source of uninitialized-ness. > But it's not actually this kzalloc, it's underlying page allocation > (that is allocated uninitialized, so can be source of > uninitialized-ness). > If it would be this kzalloc, then stack would be shorter, along the > lines of kzalloc->kmem_cache_alloc_trace->kmsan_save_stack_with_flags. > > This smells like a wild access in virtio_net_hdr_to_skb, which just > hit a random uninit somewhere. > Searching for virtio_net_hdr_to_skb I found this: > > KASAN: use-after-free Read in eth_header_parse_protocol > https://syzkaller.appspot.com/bug?id=a486048b63065fd224f57b16d5a2fdece2b40eca > > Can it be a dup of that bug? Great find. That commit is not yet present at kmsan.git at 4ebaab5fb428. Certainly sounds plausible. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb 2021-05-17 15:13 ` Willem de Bruijn @ 2021-05-17 15:44 ` Dmitry Vyukov 2021-05-17 15:44 ` syzbot 0 siblings, 1 reply; 7+ messages in thread From: Dmitry Vyukov @ 2021-05-17 15:44 UTC (permalink / raw) To: Willem de Bruijn Cc: syzbot, Andrii Nakryiko, Alexei Starovoitov, bpf, Daniel Borkmann, David Miller, Alexander Potapenko, John Fastabend, Martin Lau, KP Singh, Jakub Kicinski, linux-kernel, Network Development, Song Liu, syzkaller-bugs, Tanner Love, Xie He, Yonghong Song On Mon, May 17, 2021 at 5:13 PM Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote: > > On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <dvyukov@google.com> wrote: > > > > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn > > <willemdebruijn.kernel@gmail.com> wrote: > > > > > > On Mon, May 17, 2021 at 7:27 AM syzbot > > > <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: > > > > > > > > Hello, > > > > > > > > syzbot found the following issue on: > > > > > > > > HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. > > > > git tree: https://github.com/google/kmsan.git master > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 > > > > compiler: Debian clang version 11.0.1-2 > > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 > > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > > Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com > > > > > > > > ===================================================== > > > > BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > > > > > > No answer/fix, just initial investigation. > > > > > > This is an odd location. Line 86 is the inner if statement. Both > > > protocol and skb->protocol are clearly initialized by then. But, that > > > is also not the allocation that MSAN reports, see below. > > > > > > if (!skb->protocol) { > > > __be16 protocol = > > > dev_parse_header_protocol(skb); > > > > > > virtio_net_hdr_set_proto(skb, hdr); > > > if (protocol && protocol != skb->protocol) > > > return -EINVAL; > > > } > > > > > > The repro itself seems mostly straightforward: > > > > > > - create a packet socket > > > - enable PACKET_VNET_HDR with setsockopt(r3, 0x107, 0xf ..) > > > - bind to AF_PACKET (0x11) > > > > > > - create a pipe > > > - write to pipe[1] > > > - splice pipe[0] to the packet socket > > > > > > there are a few other calls that I think are irrelevant and/or would fail. > > > > > > Perhaps there is some race condition in device refcounting, as bind > > > operates on that? > > > > > > > CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > > > Call Trace: > > > > __dump_stack lib/dump_stack.c:79 [inline] > > > > dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 > > > > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > > > > __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 > > > > virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > > > > packet_snd net/packet/af_packet.c:2994 [inline] > > > > packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 > > > > sock_sendmsg_nosec net/socket.c:654 [inline] > > > > sock_sendmsg net/socket.c:674 [inline] > > > > kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 > > > > sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 > > > > kernel_sendpage+0x47a/0x590 net/socket.c:3631 > > > > sock_sendpage+0x161/0x1a0 net/socket.c:947 > > > > pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 > > > > splice_from_pipe_feed fs/splice.c:418 [inline] > > > > __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 > > > > splice_from_pipe fs/splice.c:597 [inline] > > > > generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 > > > > do_splice_from fs/splice.c:767 [inline] > > > > do_splice+0x23c3/0x2c10 fs/splice.c:1079 > > > > __do_splice fs/splice.c:1144 [inline] > > > > __do_sys_splice fs/splice.c:1350 [inline] > > > > __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 > > > > __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 > > > > do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 > > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > RIP: 0033:0x449a39 > > > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > > > > RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 > > > > RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 > > > > RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 > > > > RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 > > > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c > > > > R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 > > > > > > > > Uninit was created at: > > > > kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 > > > > kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 > > > > __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 > > > > alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 > > > > alloc_pages include/linux/gfp.h:561 [inline] > > > > alloc_slab_page mm/slub.c:1653 [inline] > > > > allocate_slab+0x364/0x1260 mm/slub.c:1793 > > > > new_slab mm/slub.c:1856 [inline] > > > > new_slab_objects mm/slub.c:2602 [inline] > > > > ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 > > > > __slab_alloc mm/slub.c:2805 [inline] > > > > slab_alloc_node mm/slub.c:2886 [inline] > > > > slab_alloc mm/slub.c:2931 [inline] > > > > kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 > > > > kmalloc include/linux/slab.h:554 [inline] > > > > kzalloc include/linux/slab.h:684 [inline] > > > > ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 > > > > > > This allocates ip_mc_list, but it uses kzalloc. Can that ever count as > > > uninitialized? > > > > Yes, kzalloc should never be a source of uninitialized-ness. > > But it's not actually this kzalloc, it's underlying page allocation > > (that is allocated uninitialized, so can be source of > > uninitialized-ness). > > If it would be this kzalloc, then stack would be shorter, along the > > lines of kzalloc->kmem_cache_alloc_trace->kmsan_save_stack_with_flags. > > > > This smells like a wild access in virtio_net_hdr_to_skb, which just > > hit a random uninit somewhere. > > Searching for virtio_net_hdr_to_skb I found this: > > > > KASAN: use-after-free Read in eth_header_parse_protocol > > https://syzkaller.appspot.com/bug?id=a486048b63065fd224f57b16d5a2fdece2b40eca > > > > Can it be a dup of that bug? > > Great find. > > That commit is not yet present at kmsan.git at 4ebaab5fb428. > > Certainly sounds plausible. Then let's consider: #syz dup: KASAN: use-after-free Read in eth_header_parse_protocol ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb 2021-05-17 15:44 ` Dmitry Vyukov @ 2021-05-17 15:44 ` syzbot 2021-05-17 15:46 ` Dmitry Vyukov 0 siblings, 1 reply; 7+ messages in thread From: syzbot @ 2021-05-17 15:44 UTC (permalink / raw) To: Dmitry Vyukov Cc: andrii, ast, bpf, daniel, davem, dvyukov, glider, john.fastabend, kafai, kpsingh, kuba, linux-kernel, netdev, songliubraving, syzkaller-bugs, tannerlove, willemdebruijn.kernel, xie.he.0141, yhs > On Mon, May 17, 2021 at 5:13 PM Willem de Bruijn > <willemdebruijn.kernel@gmail.com> wrote: >> >> On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <dvyukov@google.com> wrote: >> > >> > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn >> > <willemdebruijn.kernel@gmail.com> wrote: >> > > >> > > On Mon, May 17, 2021 at 7:27 AM syzbot >> > > <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: >> > > > >> > > > Hello, >> > > > >> > > > syzbot found the following issue on: >> > > > >> > > > HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. >> > > > git tree: https://github.com/google/kmsan.git master >> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 >> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 >> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 >> > > > compiler: Debian clang version 11.0.1-2 >> > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 >> > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 >> > > > >> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: >> > > > Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com >> > > > >> > > > ===================================================== >> > > > BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 >> > > >> > > No answer/fix, just initial investigation. >> > > >> > > This is an odd location. Line 86 is the inner if statement. Both >> > > protocol and skb->protocol are clearly initialized by then. But, that >> > > is also not the allocation that MSAN reports, see below. >> > > >> > > if (!skb->protocol) { >> > > __be16 protocol = >> > > dev_parse_header_protocol(skb); >> > > >> > > virtio_net_hdr_set_proto(skb, hdr); >> > > if (protocol && protocol != skb->protocol) >> > > return -EINVAL; >> > > } >> > > >> > > The repro itself seems mostly straightforward: >> > > >> > > - create a packet socket >> > > - enable PACKET_VNET_HDR with setsockopt(r3, 0x107, 0xf ..) >> > > - bind to AF_PACKET (0x11) >> > > >> > > - create a pipe >> > > - write to pipe[1] >> > > - splice pipe[0] to the packet socket >> > > >> > > there are a few other calls that I think are irrelevant and/or would fail. >> > > >> > > Perhaps there is some race condition in device refcounting, as bind >> > > operates on that? >> > > >> > > > CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 >> > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> > > > Call Trace: >> > > > __dump_stack lib/dump_stack.c:79 [inline] >> > > > dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 >> > > > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 >> > > > __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 >> > > > virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 >> > > > packet_snd net/packet/af_packet.c:2994 [inline] >> > > > packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 >> > > > sock_sendmsg_nosec net/socket.c:654 [inline] >> > > > sock_sendmsg net/socket.c:674 [inline] >> > > > kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 >> > > > sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 >> > > > kernel_sendpage+0x47a/0x590 net/socket.c:3631 >> > > > sock_sendpage+0x161/0x1a0 net/socket.c:947 >> > > > pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 >> > > > splice_from_pipe_feed fs/splice.c:418 [inline] >> > > > __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 >> > > > splice_from_pipe fs/splice.c:597 [inline] >> > > > generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 >> > > > do_splice_from fs/splice.c:767 [inline] >> > > > do_splice+0x23c3/0x2c10 fs/splice.c:1079 >> > > > __do_splice fs/splice.c:1144 [inline] >> > > > __do_sys_splice fs/splice.c:1350 [inline] >> > > > __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 >> > > > __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 >> > > > do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 >> > > > entry_SYSCALL_64_after_hwframe+0x44/0xae >> > > > RIP: 0033:0x449a39 >> > > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 >> > > > RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 >> > > > RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 >> > > > RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 >> > > > RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 >> > > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c >> > > > R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 >> > > > >> > > > Uninit was created at: >> > > > kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 >> > > > kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 >> > > > __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 >> > > > alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 >> > > > alloc_pages include/linux/gfp.h:561 [inline] >> > > > alloc_slab_page mm/slub.c:1653 [inline] >> > > > allocate_slab+0x364/0x1260 mm/slub.c:1793 >> > > > new_slab mm/slub.c:1856 [inline] >> > > > new_slab_objects mm/slub.c:2602 [inline] >> > > > ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 >> > > > __slab_alloc mm/slub.c:2805 [inline] >> > > > slab_alloc_node mm/slub.c:2886 [inline] >> > > > slab_alloc mm/slub.c:2931 [inline] >> > > > kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 >> > > > kmalloc include/linux/slab.h:554 [inline] >> > > > kzalloc include/linux/slab.h:684 [inline] >> > > > ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 >> > > >> > > This allocates ip_mc_list, but it uses kzalloc. Can that ever count as >> > > uninitialized? >> > >> > Yes, kzalloc should never be a source of uninitialized-ness. >> > But it's not actually this kzalloc, it's underlying page allocation >> > (that is allocated uninitialized, so can be source of >> > uninitialized-ness). >> > If it would be this kzalloc, then stack would be shorter, along the >> > lines of kzalloc->kmem_cache_alloc_trace->kmsan_save_stack_with_flags. >> > >> > This smells like a wild access in virtio_net_hdr_to_skb, which just >> > hit a random uninit somewhere. >> > Searching for virtio_net_hdr_to_skb I found this: >> > >> > KASAN: use-after-free Read in eth_header_parse_protocol >> > https://syzkaller.appspot.com/bug?id=a486048b63065fd224f57b16d5a2fdece2b40eca >> > >> > Can it be a dup of that bug? >> >> Great find. >> >> That commit is not yet present at kmsan.git at 4ebaab5fb428. >> >> Certainly sounds plausible. > > Then let's consider: > > #syz dup: KASAN: use-after-free Read in eth_header_parse_protocol Can't dup bug to a bug in different reporting (upstream->internal).Please dup syzbot bugs only onto syzbot bugs for the same kernel/reporting. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb 2021-05-17 15:44 ` syzbot @ 2021-05-17 15:46 ` Dmitry Vyukov 0 siblings, 0 replies; 7+ messages in thread From: Dmitry Vyukov @ 2021-05-17 15:46 UTC (permalink / raw) To: syzbot Cc: Andrii Nakryiko, Alexei Starovoitov, bpf, Daniel Borkmann, David Miller, Alexander Potapenko, John Fastabend, Martin KaFai Lau, KP Singh, Jakub Kicinski, LKML, netdev, Song Liu, syzkaller-bugs, Tanner Love, Willem de Bruijn, Xie He, Yonghong Song On Mon, May 17, 2021 at 5:44 PM syzbot <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: > > > On Mon, May 17, 2021 at 5:13 PM Willem de Bruijn > > <willemdebruijn.kernel@gmail.com> wrote: > >> > >> On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <dvyukov@google.com> wrote: > >> > > >> > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn > >> > <willemdebruijn.kernel@gmail.com> wrote: > >> > > > >> > > On Mon, May 17, 2021 at 7:27 AM syzbot > >> > > <syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com> wrote: > >> > > > > >> > > > Hello, > >> > > > > >> > > > syzbot found the following issue on: > >> > > > > >> > > > HEAD commit: 4ebaab5f kmsan: drop unneeded references to kmsan_context_.. > >> > > > git tree: https://github.com/google/kmsan.git master > >> > > > console output: https://syzkaller.appspot.com/x/log.txt?x=17ac508ed00000 > >> > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ab8076fe8508c0d3 > >> > > > dashboard link: https://syzkaller.appspot.com/bug?extid=106457891e3cf3b273a9 > >> > > > compiler: Debian clang version 11.0.1-2 > >> > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=138f4972d00000 > >> > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1624ffced00000 > >> > > > > >> > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > >> > > > Reported-by: syzbot+106457891e3cf3b273a9@syzkaller.appspotmail.com > >> > > > > >> > > > ===================================================== > >> > > > BUG: KMSAN: uninit-value in virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > >> > > > >> > > No answer/fix, just initial investigation. > >> > > > >> > > This is an odd location. Line 86 is the inner if statement. Both > >> > > protocol and skb->protocol are clearly initialized by then. But, that > >> > > is also not the allocation that MSAN reports, see below. > >> > > > >> > > if (!skb->protocol) { > >> > > __be16 protocol = > >> > > dev_parse_header_protocol(skb); > >> > > > >> > > virtio_net_hdr_set_proto(skb, hdr); > >> > > if (protocol && protocol != skb->protocol) > >> > > return -EINVAL; > >> > > } > >> > > > >> > > The repro itself seems mostly straightforward: > >> > > > >> > > - create a packet socket > >> > > - enable PACKET_VNET_HDR with setsockopt(r3, 0x107, 0xf ..) > >> > > - bind to AF_PACKET (0x11) > >> > > > >> > > - create a pipe > >> > > - write to pipe[1] > >> > > - splice pipe[0] to the packet socket > >> > > > >> > > there are a few other calls that I think are irrelevant and/or would fail. > >> > > > >> > > Perhaps there is some race condition in device refcounting, as bind > >> > > operates on that? > >> > > > >> > > > CPU: 0 PID: 8426 Comm: syz-executor777 Not tainted 5.12.0-rc6-syzkaller #0 > >> > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > >> > > > Call Trace: > >> > > > __dump_stack lib/dump_stack.c:79 [inline] > >> > > > dump_stack+0x24c/0x2e0 lib/dump_stack.c:120 > >> > > > kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118 > >> > > > __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197 > >> > > > virtio_net_hdr_to_skb+0x1414/0x14f0 include/linux/virtio_net.h:86 > >> > > > packet_snd net/packet/af_packet.c:2994 [inline] > >> > > > packet_sendmsg+0x85b8/0x99d0 net/packet/af_packet.c:3031 > >> > > > sock_sendmsg_nosec net/socket.c:654 [inline] > >> > > > sock_sendmsg net/socket.c:674 [inline] > >> > > > kernel_sendmsg+0x22c/0x2f0 net/socket.c:694 > >> > > > sock_no_sendpage+0x205/0x2b0 net/core/sock.c:2860 > >> > > > kernel_sendpage+0x47a/0x590 net/socket.c:3631 > >> > > > sock_sendpage+0x161/0x1a0 net/socket.c:947 > >> > > > pipe_to_sendpage+0x3e4/0x520 fs/splice.c:364 > >> > > > splice_from_pipe_feed fs/splice.c:418 [inline] > >> > > > __splice_from_pipe+0x5e3/0xff0 fs/splice.c:562 > >> > > > splice_from_pipe fs/splice.c:597 [inline] > >> > > > generic_splice_sendpage+0x1d5/0x2c0 fs/splice.c:746 > >> > > > do_splice_from fs/splice.c:767 [inline] > >> > > > do_splice+0x23c3/0x2c10 fs/splice.c:1079 > >> > > > __do_splice fs/splice.c:1144 [inline] > >> > > > __do_sys_splice fs/splice.c:1350 [inline] > >> > > > __se_sys_splice+0x8fa/0xb50 fs/splice.c:1332 > >> > > > __x64_sys_splice+0x6e/0x90 fs/splice.c:1332 > >> > > > do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48 > >> > > > entry_SYSCALL_64_after_hwframe+0x44/0xae > >> > > > RIP: 0033:0x449a39 > >> > > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > >> > > > RSP: 002b:00007f8ed790b2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 > >> > > > RAX: ffffffffffffffda RBX: 00000000004cf518 RCX: 0000000000449a39 > >> > > > RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 > >> > > > RBP: 00000000004cf510 R08: 000000000004ffe0 R09: 0000000000000000 > >> > > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf51c > >> > > > R13: 000000000049e46c R14: 6d32cc5e8ead0600 R15: 0000000000022000 > >> > > > > >> > > > Uninit was created at: > >> > > > kmsan_save_stack_with_flags+0x3c/0x90 mm/kmsan/kmsan.c:121 > >> > > > kmsan_alloc_page+0xd0/0x1e0 mm/kmsan/kmsan_shadow.c:274 > >> > > > __alloc_pages_nodemask+0x827/0xf90 mm/page_alloc.c:5044 > >> > > > alloc_pages_current+0x7b6/0xb60 mm/mempolicy.c:2277 > >> > > > alloc_pages include/linux/gfp.h:561 [inline] > >> > > > alloc_slab_page mm/slub.c:1653 [inline] > >> > > > allocate_slab+0x364/0x1260 mm/slub.c:1793 > >> > > > new_slab mm/slub.c:1856 [inline] > >> > > > new_slab_objects mm/slub.c:2602 [inline] > >> > > > ___slab_alloc+0xd42/0x1930 mm/slub.c:2765 > >> > > > __slab_alloc mm/slub.c:2805 [inline] > >> > > > slab_alloc_node mm/slub.c:2886 [inline] > >> > > > slab_alloc mm/slub.c:2931 [inline] > >> > > > kmem_cache_alloc_trace+0xc53/0x1030 mm/slub.c:2948 > >> > > > kmalloc include/linux/slab.h:554 [inline] > >> > > > kzalloc include/linux/slab.h:684 [inline] > >> > > > ____ip_mc_inc_group+0x4d7/0x10b0 net/ipv4/igmp.c:1435 > >> > > > >> > > This allocates ip_mc_list, but it uses kzalloc. Can that ever count as > >> > > uninitialized? > >> > > >> > Yes, kzalloc should never be a source of uninitialized-ness. > >> > But it's not actually this kzalloc, it's underlying page allocation > >> > (that is allocated uninitialized, so can be source of > >> > uninitialized-ness). > >> > If it would be this kzalloc, then stack would be shorter, along the > >> > lines of kzalloc->kmem_cache_alloc_trace->kmsan_save_stack_with_flags. > >> > > >> > This smells like a wild access in virtio_net_hdr_to_skb, which just > >> > hit a random uninit somewhere. > >> > Searching for virtio_net_hdr_to_skb I found this: > >> > > >> > KASAN: use-after-free Read in eth_header_parse_protocol > >> > https://syzkaller.appspot.com/bug?id=a486048b63065fd224f57b16d5a2fdece2b40eca > >> > > >> > Can it be a dup of that bug? > >> > >> Great find. > >> > >> That commit is not yet present at kmsan.git at 4ebaab5fb428. > >> > >> Certainly sounds plausible. > > > > Then let's consider: > > > > #syz dup: KASAN: use-after-free Read in eth_header_parse_protocol > > Can't dup bug to a bug in different reporting (upstream->internal).Please dup syzbot bugs only onto syzbot bugs for the same kernel/reporting. Let's try: #syz fix: net: ensure mac header is set in virtio_net_hdr_to_skb() ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-05-17 16:40 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-05-17 11:27 [syzbot] KMSAN: uninit-value in virtio_net_hdr_to_skb syzbot 2021-05-17 14:05 ` Willem de Bruijn 2021-05-17 14:21 ` Dmitry Vyukov 2021-05-17 15:13 ` Willem de Bruijn 2021-05-17 15:44 ` Dmitry Vyukov 2021-05-17 15:44 ` syzbot 2021-05-17 15:46 ` Dmitry Vyukov
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