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SubjectRe: BUG: unable to handle kernel paging request at ffffe8ff7fc00001
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On Sun, Nov 15, 2015 at 2:28 PM, Kyle Sanderson <kyle.leet@gmail.com> wrote:
> [] BUG: unable to handle kernel paging request at ffffe8ff7fc00001
> [] IP: [<ffffffff810a174f>] kstat_irqs+0x4f/0x90
> [] CPU: 2 PID: 1078 Comm: usage.pl Not tainted 4.1.7-hardened-r1 #1
> [] Hardware name: Supermicro Super Server/X10SRi-F, BIOS 1.0b 04/21/2015
RSI: 000060f700000001
> [] Call Trace:
> [] [<>] kstat_irqs_usr+0x1e/0x40
> [] [<>] show_stat+0x5ca/0x690
> [] [<>] seq_read+0xcd/0x3b0
> [] [<>] proc_reg_read+0x43/0x70
> [] [<>] __vfs_read+0x23/0xd0
> [] [<>] vfs_read+0xc0/0x1d0
> [] [<>] SyS_read+0x41/0xb0
> [] [<>] system_call_fastpath+0x16/0x72
> [] Code: 83 78 48 00 74 56 4c 8b ...

The code ends up being

mov 0x48(%r13),%rsi
mov __per_cpu_offset(,%rcx,8),%rcx
add (%rsi,%rcx,1),%ebx <-- trapping instruction

which is just the

sum += *per_cpu_ptr(desc->kstat_irqs, cpu);

part of kstat_irqs().

Your registers being

RSI: 000060f700000001
RCX: ffff88087fc00000

and it's RSI that makes no sense - RCX looks like a real kernel
pointer. So it looks like it's the "desc->kstat_irqs" thing that is
for some reason garbage.

I don't see any sane possible reason this would happen, though.
Thomas, does this look like anything you've seen before?

Linus


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