Re: [Xen-devel] [PATCH] ioemu block device extent checks

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Daniel P. Berrange writes ("Re: [Xen-devel] [PATCH] ioemu block device extent 
checks"):
> I don't think this is correct - it allows a -ve  size / nb_sectors
> value when autoextenable is set, and allows out of bounds reads.

That's fine because it's only called like that as a the parent block
driver.  Perhaps a different name would have been better.

Out of bounds reads have to be permitted because the block size in the
header may remain un-updated, so reads of newly-cloned blocks may
fail.

> I sent a patch to qemu-devel yuesterday which also uses the auto-extend
> flag, but has separate checks for read vs writes. When doing a write that
> would extend the device it increases the total_sectors count so that the
> subsequent reads can be validated to be within the written bounds.

Well, that seems like makework to me but fine if upstream accept it.

Ian.

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