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Commit daeba295 authored by Russell Currey's avatar Russell Currey Committed by Michael Ellerman
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powerpc/eeh: Avoid use after free in eeh_handle_special_event() 



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().

Fixes: 8a6b1bc7 ("powerpc/eeh: EEH core to handle special event")
Cc: stable@vger.kernel.org # v3.11+
Reported-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: default avatarRussell Currey <ruscur@russell.cc>
Reviewed-by: default avatarGavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent a715626a

arch/powerpc/kernel/eeh_driver.c

+15 −4
Original line number Diff line number Diff line
@@ -724,7 +724,7 @@ static int eeh_reset_device(struct eeh_pe *pe, struct pci_bus *bus, 
 */

#define MAX_WAIT_FOR_RECOVERY 300



static void eeh_handle_normal_event(struct eeh_pe *pe)

static bool eeh_handle_normal_event(struct eeh_pe *pe)

{

	struct pci_bus *frozen_bus;

	struct eeh_dev *edev, *tmp;
@@ -736,7 +736,7 @@ static void eeh_handle_normal_event(struct eeh_pe *pe) 
	if (!frozen_bus) {

		pr_err("%s: Cannot find PCI bus for PHB#%x-PE#%x\n",

			__func__, pe->phb->global_number, pe->addr);

		return;

		return false;

	}



	eeh_pe_update_time_stamp(pe);
@@ -870,7 +870,7 @@ static void eeh_handle_normal_event(struct eeh_pe *pe) 
	pr_info("EEH: Notify device driver to resume\n");

	eeh_pe_dev_traverse(pe, eeh_report_resume, NULL);



	return;

	return false;



excess_failures:

	/*
@@ -915,8 +915,12 @@ static void eeh_handle_normal_event(struct eeh_pe *pe) 
			pci_lock_rescan_remove();

			pci_hp_remove_devices(frozen_bus);

			pci_unlock_rescan_remove();



			/* The passed PE should no longer be used */

			return true;

		}

	}

	return false;

}



static void eeh_handle_special_event(void)
@@ -982,7 +986,14 @@ static void eeh_handle_special_event(void) 
		 */

		if (rc == EEH_NEXT_ERR_FROZEN_PE ||

		    rc == EEH_NEXT_ERR_FENCED_PHB) {

			eeh_handle_normal_event(pe);

			/*

			 * eeh_handle_normal_event() can make the PE stale if it

			 * determines that the PE cannot possibly be recovered.

			 * Don't modify the PE state if that's the case.

			 */

			if (eeh_handle_normal_event(pe))

				continue;



			eeh_pe_state_clear(pe, EEH_PE_RECOVERING);

		} else {

			pci_lock_rescan_remove();