linux-kernel - [PATCH 3.16 104/134] powerpc/eeh: Avoid use after free in eeh_handle_special

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1503062000.817722530@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Michael Ellerman" <mpe@...erman.id.au>,
        "Russell Currey" <ruscur@...sell.cc>,
        "Gavin Shan" <gwshan@...ux.vnet.ibm.com>,
        "Alexey Kardashevskiy" <aik@...abs.ru>
Subject: [PATCH 3.16 104/134] powerpc/eeh: Avoid use after free in
 eeh_handle_special_event()

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Russell Currey <ruscur@...sell.cc>

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 <aik@...abs.ru>
Signed-off-by: Russell Currey <ruscur@...sell.cc>
Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
[bwh: Backported to 3.16: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -584,7 +584,7 @@ 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;
@@ -594,7 +594,7 @@ 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);
@@ -711,7 +711,7 @@ 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:
 	/*
@@ -751,7 +751,11 @@ 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)
@@ -817,7 +821,14 @@ 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();