linux-kernel - [PATCH 3.12 087/113] goldfish: Sanitize the broken interrupt handler

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Message-Id: <94e5bdac8a29138a96e560a8c8d4607e2d8d9e20.1488791431.git.jslaby@suse.cz>
Date:   Mon,  6 Mar 2017 10:11:51 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 087/113] goldfish: Sanitize the broken interrupt handler

From: Thomas Gleixner <tglx@...utronix.de>

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

===============

commit 6cf18e6927c0b224f972e3042fb85770d63cb9f8 upstream.

This interrupt handler is broken in several ways:

  - It loops forever when the op code is not decodeable

  - It never returns IRQ_HANDLED because the only way to exit the loop
    returns IRQ_NONE unconditionally.

The whole concept of this is broken. Creating devices in an interrupt
handler is beyond any point of sanity.

Make it at least behave halfways sane so accidental users do not have to
deal with a hard to debug lockup.

Fixes: e809c22b8fb028 ("goldfish: add the goldfish virtual bus")
Reported-by: Gabriel C <nix.or.die@...il.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/platform/goldfish/pdev_bus.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/platform/goldfish/pdev_bus.c b/drivers/platform/goldfish/pdev_bus.c
index 92cc4cfafde5..6bcd57cb2f75 100644
--- a/drivers/platform/goldfish/pdev_bus.c
+++ b/drivers/platform/goldfish/pdev_bus.c
@@ -153,23 +153,26 @@ static int goldfish_new_pdev(void)
 static irqreturn_t goldfish_pdev_bus_interrupt(int irq, void *dev_id)
 {
 	irqreturn_t ret = IRQ_NONE;
+
 	while (1) {
 		u32 op = readl(pdev_bus_base + PDEV_BUS_OP);
-		switch (op) {
-		case PDEV_BUS_OP_DONE:
-			return IRQ_NONE;
 
+		switch (op) {
 		case PDEV_BUS_OP_REMOVE_DEV:
 			goldfish_pdev_remove();
+			ret = IRQ_HANDLED;
 			break;
 
 		case PDEV_BUS_OP_ADD_DEV:
 			goldfish_new_pdev();
+			ret = IRQ_HANDLED;
 			break;
+
+		case PDEV_BUS_OP_DONE:
+		default:
+			return ret;
 		}
-		ret = IRQ_HANDLED;
 	}
-	return ret;
 }
 
 static int goldfish_pdev_bus_probe(struct platform_device *pdev)
-- 
2.12.0