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official usermode thread support in LKL #250

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M1cha opened this issue Oct 14, 2016 · 0 comments
Open

official usermode thread support in LKL #250

M1cha opened this issue Oct 14, 2016 · 0 comments

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@M1cha
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M1cha commented Oct 14, 2016

I am working on adding user level threads support (for the idle and various kernel threads) to see if we can boost the performance further and also make it easier for other thread-less environments (like UEFI) but I didn't get a chance to merge it with the "host tasks" patches. Once I do that, we should run into the same issue you do and be able to help.

I thought I'd open a new issue for that to not bloat the direct host call PR.

@tavip how does your solution work? Did you write your own threading library or did you find a good one which you can use in lkl?

I'd also be happy to help improving/testing your code
@thehajime thehajime mentioned this issue Oct 28, 2016
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@M1cha M1cha mentioned this issue Oct 29, 2016
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@thehajime thehajime mentioned this issue Feb 15, 2017
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thehajime pushed a commit to libos-nuse/lkl-linux that referenced this issue Oct 11, 2017
@davem330
net: ipv6: RTF_PCPU should not be settable from userspace
557c44b 
Andrey reported a fault in the IPv6 route code:

kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 1 PID: 4035 Comm: a.out Not tainted 4.11.0-rc7+ lkl#250
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff880069809600 task.stack: ffff880062dc8000
RIP: 0010:ip6_rt_cache_alloc+0xa6/0x560 net/ipv6/route.c:975
RSP: 0018:ffff880062dced30 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff8800670561c0 RCX: 0000000000000006
RDX: 0000000000000003 RSI: ffff880062dcfb28 RDI: 0000000000000018
RBP: ffff880062dced68 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff880062dcfb28 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007feebe37e7c0(0000) GS:ffff88006cb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000205a0fe4 CR3: 000000006b5c9000 CR4: 00000000000006e0
Call Trace:
 ip6_pol_route+0x1512/0x1f20 net/ipv6/route.c:1128
 ip6_pol_route_output+0x4c/0x60 net/ipv6/route.c:1212
...

Andrey's syzkaller program passes rtmsg.rtmsg_flags with the RTF_PCPU bit
set. Flags passed to the kernel are blindly copied to the allocated
rt6_info by ip6_route_info_create making a newly inserted route appear
as though it is a per-cpu route. ip6_rt_cache_alloc sees the flag set
and expects rt->dst.from to be set - which it is not since it is not
really a per-cpu copy. The subsequent call to __ip6_dst_alloc then
generates the fault.

Fix by checking for the flag and failing with EINVAL.

Fixes: d52d399 ("ipv6: Create percpu rt6_info")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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