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Date: Tue, 30 Oct 2001 20:13:51 -0500 (EST)
From: Alexander Viro <viro@math.psu.edu>
To: Linus Torvalds <torvalds@transmeta.com>
cc: airlied@csn.ul.ie, linux-kernel@vger.kernel.org
Subject: Re: oops on 2.4.13-pre5 in prune_dcache
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On Tue, 30 Oct 2001, Linus Torvalds wrote:

> It's almost certainly _supposed_ to be a NULL pointer, but has bit 6
> set. 
> 
> So we do
> 
> 	if (dentry->d_op && dentry->d_op->d_iput)
> 
> and because dentry->d_op isn't NULL, we oops on the d_op->d_iput
> dereference.
> 
> Something is setting a bit in your dentry. Either RAM errors (do you
> have ECC memory or a history of SIGSEGV's to give any indication either
> way?) or a wild "set_bit()" pointer or similar.

... or corrupted pointer in the list, in which case we are at the address
that had never been a dentry.

Frankly, it looks like adding magic to struct dentry and struct inode
might be a good idea.  Both icache and dcache lists tend to be long,
so any memory corruption is very likely to show up in the code that
walks them.

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