3.18-stable review patch. If anyone has any objections, please let me know.
------------------ From: Russell Currey <[email protected]> commit daeba2956f32f91f3493788ff6ee02fb1b2f02fa upstream. 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: 8a6b1bc70dbb ("powerpc/eeh: EEH core to handle special event") Reported-by: Alexey Kardashevskiy <[email protected]> Signed-off-by: Russell Currey <[email protected]> Reviewed-by: Gavin Shan <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/powerpc/kernel/eeh_driver.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) --- a/arch/powerpc/kernel/eeh_driver.c +++ b/arch/powerpc/kernel/eeh_driver.c @@ -678,7 +678,7 @@ static int eeh_reset_device(struct eeh_p */ #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; int rc = 0; @@ -688,7 +688,7 @@ static void eeh_handle_normal_event(stru if (!frozen_bus) { pr_err("%s: Cannot find PCI bus for PHB#%d-PE#%x\n", __func__, pe->phb->global_number, pe->addr); - return; + return false; } eeh_pe_update_time_stamp(pe); @@ -805,7 +805,7 @@ static void eeh_handle_normal_event(stru pr_info("EEH: Notify device driver to resume\n"); eeh_pe_dev_traverse(pe, eeh_report_resume, NULL); - return; + return false; excess_failures: /* @@ -845,7 +845,11 @@ perm_error: pci_lock_rescan_remove(); pcibios_remove_pci_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) @@ -911,7 +915,14 @@ static void eeh_handle_special_event(voi */ 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();
