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: [email protected]
=====================================================
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
=====================================================
---
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On Mon, May 17, 2021 at 7:27 AM syzbot
<[email protected]> 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: [email protected]
>
> =====================================================
> 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?
On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn
<[email protected]> wrote:
>
> On Mon, May 17, 2021 at 7:27 AM syzbot
> <[email protected]> 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: [email protected]
> >
> > =====================================================
> > 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?
> On Mon, May 17, 2021 at 5:13 PM Willem de Bruijn
> <[email protected]> wrote:
>>
>> On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <[email protected]> wrote:
>> >
>> > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn
>> > <[email protected]> wrote:
>> > >
>> > > On Mon, May 17, 2021 at 7:27 AM syzbot
>> > > <[email protected]> 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: [email protected]
>> > > >
>> > > > =====================================================
>> > > > 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.
On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <[email protected]> wrote:
>
> On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn
> <[email protected]> wrote:
> >
> > On Mon, May 17, 2021 at 7:27 AM syzbot
> > <[email protected]> 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: [email protected]
> > >
> > > =====================================================
> > > 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.
On Mon, May 17, 2021 at 5:13 PM Willem de Bruijn
<[email protected]> wrote:
>
> On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <[email protected]> wrote:
> >
> > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn
> > <[email protected]> wrote:
> > >
> > > On Mon, May 17, 2021 at 7:27 AM syzbot
> > > <[email protected]> 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: [email protected]
> > > >
> > > > =====================================================
> > > > 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
On Mon, May 17, 2021 at 5:44 PM syzbot
<[email protected]> wrote:
>
> > On Mon, May 17, 2021 at 5:13 PM Willem de Bruijn
> > <[email protected]> wrote:
> >>
> >> On Mon, May 17, 2021 at 10:57 AM Dmitry Vyukov <[email protected]> wrote:
> >> >
> >> > On Mon, May 17, 2021 at 4:06 PM Willem de Bruijn
> >> > <[email protected]> wrote:
> >> > >
> >> > > On Mon, May 17, 2021 at 7:27 AM syzbot
> >> > > <[email protected]> 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: [email protected]
> >> > > >
> >> > > > =====================================================
> >> > > > 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()