On Tuesday September 11, [EMAIL PROTECTED] wrote:
> This oops appeared over night on a box running 2.6.23-rc5 (recent with the
> tcp_input.c fix).
>
> I can't find a similar one reported.
Okay..... this is weird.
>
> Mark
>
>
> BUG: unable to handle kernel NULL pointer dereference at virtual address
> 0000007e
^^^^^^^^
That is the bad address,
> EFLAGS: 00010246 (2.6.23-rc5-2-mcyrixiii #1)
> EIP is at ip_fragment+0x7f/0x680
> eax: c3c09c00 ebx: 00000000 ecx: b524d006 edx: 0000007b
^^^^^^^^^^^^^
It looks like an offset of 3 from edx. I got that from decoding:
> Code: .... <00> ba 03 00 00 00 bf a6 ff ff
which is
0: 00 ba 03 00 00 00 add %bh,0x3(%rdx)
However that instruction doesn't appear in ip_fragment.
The code in ip_fragment reads:
27: b9 04 00 00 00 mov $0x4,%ecx
^^
2c: ba 03 00 00 00 mov $0x3,%edx
^^^^^^^^^^^^^^
which contains the bytes of the offending instruction.
Note that $0x4 is ICMP_FRAG_NEEDED and $0x3 is ICMP_DEST_UNREACH:
these are args to icmp_send. So the latter is the correct disassembly
based on the C code.
So somehow the kernel is jumping to a bad address. I don't know how
that would happening.... maybe a single bit error in memory or a
register???
NeilBrown
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