Re: [OOPS] 2.6.23-rc5 in tcp/net/nfsd

2007-09-11 Thread Neil Brown 
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 
 007e 
   


That is the bad address,

 EFLAGS: 00010246   (2.6.23-rc5-2-mcyrixiii #1)
 EIP is at ip_fragment+0x7f/0x680
 eax: c3c09c00   ebx:    ecx: b524d006   edx: 007b
  ^

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 00mov$0x4,%ecx
^^
  2c:   ba 03 00 00 00mov$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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Re: [OOPS] 2.6.23-rc5 in tcp/net/nfsd

2007-09-11 Thread Herbert Xu 
Mark Hindley [EMAIL PROTECTED] wrote:

 Code: 01 00 00 03 75 0e 8b 42 18 8b 40 0c 8b 80 c4 00 00 00 eb 0a 8b 4c 24 08 
 8b 41 18 8b 40 28 0f c8 89 04 24 8b 44 24 08 b9 04 00 00 00 ba 03 00 00 00 
 bf a6 ff ff
 EIP: [c02625bf] ip_fragment+0x7f/0x680 SS:ESP 0068:ccb48b3c

The EIP is off by one byte.  So either a hardware problem or a
really unlikely result of stack corruption.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmVHI~} [EMAIL PROTECTED]
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