Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755223AbdFLQE5 (ORCPT ); Mon, 12 Jun 2017 12:04:57 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42786 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755206AbdFLPkH (ORCPT ); Mon, 12 Jun 2017 11:40:07 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexey Kardashevskiy , Russell Currey , Gavin Shan , Michael Ellerman Subject: [PATCH 4.4 65/90] powerpc/eeh: Avoid use after free in eeh_handle_special_event() Date: Mon, 12 Jun 2017 17:26:11 +0200 Message-Id: <20170612152600.819354254@linuxfoundation.org> X-Mailer: git-send-email 2.13.1 In-Reply-To: <20170612152556.133240249@linuxfoundation.org> References: <20170612152556.133240249@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2925 Lines: 91 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Russell Currey 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 Signed-off-by: Russell Currey Reviewed-by: Gavin Shan Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- 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 @@ -655,7 +655,7 @@ 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; @@ -665,7 +665,7 @@ 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); @@ -790,7 +790,7 @@ 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: /* @@ -831,7 +831,11 @@ 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) @@ -897,7 +901,14 @@ 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();