[PATCH v3 1/2] powerpc/eeh: Avoid use after free in eeh_handle_special_event()

[Gavin Shan]

On Wed, Apr 19, 2017 at 05:39:26PM +1000, Russell Currey wrote:
>eeh_handle_special_event() is called when an EEH event is detected but
>can't be narrowed down to a specific PE.  This function looks through
>every PE to find one in an erroneous state, then calls the regular event
>handler eeh_handle_normal_event() once it knows which PE has an error.
>
>However, if eeh_handle_normal_event() found that the PE cannot possibly
>be recovered, it will free it, rendering the passed PE stale.
>This leads to a use after free in eeh_handle_special_event() as it attempts to
>clear the "recovering" state on the PE after eeh_handle_normal_event() returns.
>
>Thus, make sure the PE is valid when attempting to clear state in
>eeh_handle_special_event().
>
>Cc: <stable at vger.kernel.org> #3.10+
>Reported-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>Signed-off-by: Russell Currey <ruscur at russell.cc>

Reviewed-by: Gavin Shan <gwshan at linux.vnet.ibm.com>