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SubjectRe: [PATCH] kvm: Prevent kvm_init from corrupting debugfs structures
On Wed, Oct 14, 2009 at 04:21:00PM -0700, Darrick J. Wong wrote:
> I'm seeing an oops condition when kvm-intel and kvm-amd are modprobe'd
> during boot (say on an Intel system) and then rmmod'd:
>
> # modprobe kvm-intel
> kvm_init()
> kvm_init_debug()
> kvm_arch_init() <-- stores debugfs dentries internally
> (success, etc)
>
> # modprobe kvm-amd
> kvm_init()
> kvm_init_debug() <-- second initialization clobbers kvm's
> internal pointers to dentries
> kvm_arch_init()
> kvm_exit_debug() <-- and frees them
>
> # rmmod kvm-intel
> kvm_exit()
> kvm_exit_debug() <-- double free of debugfs files!
>
> *BOOM*
>
> If execution gets to the end of kvm_init(), then the calling module has been
> established as the kvm provider. Move the debugfs initialization to the end of
> the function, and remove the now-unnecessary call to kvm_exit_debug() from the
> error path. That way we avoid trampling on the debugfs entries and freeing
> them twice.
>
> Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>

Applied, thanks.



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