linux-kernel - [PATCH 4.17 053/336] powerpc/eeh: Fix use-after-release of EEH driver

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Date:   Wed,  1 Aug 2018 18:46:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sam Bobroff <sbobroff@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.17 053/336] powerpc/eeh: Fix use-after-release of EEH driver

4.17-stable review patch.  If anyone has any objections, please let me know.

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

From: Sam Bobroff <sbobroff@...ux.ibm.com>

[ Upstream commit 46d4be41b987a6b2d25a2ebdd94cafb44e21d6c5 ]

Correct two cases where eeh_pcid_get() is used to reference the driver's
module but the reference is dropped before the driver pointer is used.

In eeh_rmv_device() also refactor a little so that only two calls to
eeh_pcid_put() are needed, rather than three and the reference isn't
taken at all if it wasn't needed.

Signed-off-by: Sam Bobroff <sbobroff@...ux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/powerpc/kernel/eeh_driver.c |   28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -458,9 +458,11 @@ static void *eeh_add_virt_device(void *d
 
 	driver = eeh_pcid_get(dev);
 	if (driver) {
-		eeh_pcid_put(dev);
-		if (driver->err_handler)
+		if (driver->err_handler) {
+			eeh_pcid_put(dev);
 			return NULL;
+		}
+		eeh_pcid_put(dev);
 	}
 
 #ifdef CONFIG_PCI_IOV
@@ -497,17 +499,19 @@ static void *eeh_rmv_device(void *data,
 	if (eeh_dev_removed(edev))
 		return NULL;
 
-	driver = eeh_pcid_get(dev);
-	if (driver) {
-		eeh_pcid_put(dev);
-		if (removed &&
-		    eeh_pe_passed(edev->pe))
-			return NULL;
-		if (removed &&
-		    driver->err_handler &&
-		    driver->err_handler->error_detected &&
-		    driver->err_handler->slot_reset)
+	if (removed) {
+		if (eeh_pe_passed(edev->pe))
 			return NULL;
+		driver = eeh_pcid_get(dev);
+		if (driver) {
+			if (driver->err_handler &&
+			    driver->err_handler->error_detected &&
+			    driver->err_handler->slot_reset) {
+				eeh_pcid_put(dev);
+				return NULL;
+			}
+			eeh_pcid_put(dev);
+		}
 	}
 
 	/* Remove it from PCI subsystem */