Re: decnet versions

[Steve Whitehouse <steve@gw.chygwyn.com>]

Hi,

Thanks for the crash dump & analysis.
My best guess is that its down to a shortage of memory... I wonder how much
free memory there was at the time ? I've noticed that there appears to be
no checks against alloc_skb(size, GFP_ATOMIC) returning NULL which it will
almost certainly do at some stage unless the box is very lightly loaded.
Perhaps there might be alot of other net traffic which may be using up the
atomicly allocatable memory.

The fix is to return NULL from dn_alloc_skb() if alloc_skb() 
returned a NULL pointer, and to allow for NULL pointers in each function
which calls dn_alloc_skb() too. Ok, it might not be the cause of this 
particular crash, but it will certainly cause problems if it is not fixed,

Steve.

> 
> On Sat, 22 Jan 2000, Zane H. Healy wrote:
>   
>   As a newcomer let me introduce myself, Kevin Hannan.  I hope to be of some
> help here.  Soon I will have hardware in place to begin helping.  In the
> meantime I'll mainly try to catch up and help when possible.
> 
>   For my 2 cents on this... It appears to be an offset into a structure with
> either 2 pointers or longs, or some other mixture + alignment to equal 8 bytes.
> All this occurring in dn_send_disc near the end of the function (close to
> dn_nsp_disc_init).  Also, ck_free and sock_wfree are next up the stack.
>   This is just a guess, but I hope it gives some insight/assistance.
> 
>   Kevin
> 
> > On the Linux box:
> > 2.2.14 Kernel w/decnet2214.diff
> > Running Red Hat 6.1
> > dnprogs-2.03.tar.gz
> > 
> > Unable to handle kernel NULL pointer dereference at virtual address 00000008
> > current->tss.cr3 = 00101000, %cr3 = 00101000
> > *pde = 00000000
> > Oops: 0000
> > CPU:    0
> > EIP:    0010:[<c0120408>]
> > EFLAGS: 00010082
> > eax: 0000037c   ebx: cc9a6e00   ecx: 00000000   edx: cc9a717c
> > esi: cdfff860   edi: 00000286   ebp: 00000001   esp: cd0a3e58
> > ds: 0018   es: 0018   ss: 0018
> > Process dnetd (pid: 142, process nr: 11, stacckpage=cd0a3000)
> > Stack: cc9a6e00 00000001 cc9a717c c0194564 c0166bf1 cdfff860 cc9a6e00 00000000
> >        c0192e9b cc9a6e00 cc9a6e00 cd0682c0 cc4195c0 c0193303 cc9a6e00 cc9a6e00
> >        cd0682c0 cd068224 c0164ff7 cd0682c0 00000000 cd068224 c01653d1 cd0682c0
> > Call Trace: [<c0194564>] [<c0166bf1>] [<c0192e9b>] [<c0193303>]
> > [<c0164ff7>] [<c01653d1>] [<c01249cf>]
> >        [<c0125bb7>] [<c0124a4a>] [<c0116b2b>] [<c0107928>] [<c010f9a8>]
> > [<c010fbf1>] [<c010efa8>] [<c0107b55>]
> >        [<c0107a98>]
> > Code: 8b 69 08 81 fd 2b 2f c3 a5 0f 85 ed 00 00 00 8b 69 0c 85 ed
> > 
> > -----------------------------------------------------------------------------
> 

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