From: Arnd Bergmann <arnd@arndb.de>
To: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Subject: Re: [PATCH 00/10] AXFS: Advanced XIP filesystem
Date: Fri, 22 Aug 2008 17:19:06 +0200
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On Friday 22 August 2008, Geert Uytterhoeven wrote:
> I gave AxFS a try on PS3 (ppc64, always use big-endian 64-bit for testing new
> code ;-).
> When mounting the image, I got the crash below:
> 
> | attempt to access beyond end of device
> | loop0: rw=0, want=4920, limit=4912
> | Unable to handle kernel paging request for data at address 0x00000028


Offset 0x28 is buffer_head->b_data, so it seems like sb_bread returns NULL,
which it does for out of range block numbers. I guess axfs_copy_block
should check for that condition, as it can happen on malicious file system
images.
I agree that this is likely to get caused by an endianess bug.
A good help for finding endianess bugs is to use __be64 like data types
everywhere and test with sparse -D__CHECK_ENDIAN__.

	Arnd 
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