Date:   Tue, 30 Aug 2022 14:54:13 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Russell King <linux@...linux.org.uk>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <patches@...linux.org.uk>
CC:     Zhen Lei <thunder.leizhen@...wei.com>,
        Saravana Kannan <saravanak@...gle.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        "Linus Walleij" <linus.walleij@...aro.org>
Subject: [PATCH v2] ARM: Add sanity check for dev->periphid in amba_probe()

Commit f2d3b9a46e0e ("ARM: 9220/1: amba: Remove deferred device addition")
forcibly invokes device_add() even if dev->periphid is not ready. Although
it will be remedied in amba_match(): dev->periphid will be initialized
if everything is in place; Otherwise, return -EPROBE_DEFER to block
__driver_attach() from further execution. But not all drivers have .match
hook, such as pl031, the dev->bus->probe will be called directly in
__driver_attach(). Unfortunately, if dev->periphid is still not
initialized, the following exception will be triggered.

8<--- cut here ---
Unable to handle kernel NULL pointer dereference at virtual address 00000008
[00000008] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.0.0-rc2+ #7
Hardware name: ARM-Versatile Express
PC is at pl031_probe+0x8/0x208
LR is at amba_probe+0xf0/0x160
pc : 80698df8  lr : 8050eb54  psr: 80000013
sp : c0825df8  ip : 00000000  fp : 811fda38
r10: 00000000  r9 : 80d72470  r8 : fffffdfb
r7 : 811fd800  r6 : be7eb330  r5 : 00000000  r4 : 811fd900
r3 : 80698df0  r2 : 37000000  r1 : 00000000  r0 : 811fd800
Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 10c5387d  Table: 6000406a  DAC: 00000051
... ...
 pl031_probe from amba_probe+0xf0/0x160
 amba_probe from really_probe+0x118/0x290
 really_probe from __driver_probe_device+0x84/0xe4
 __driver_probe_device from driver_probe_device+0x30/0xd0
 driver_probe_device from __driver_attach+0x8c/0xfc
 __driver_attach from bus_for_each_dev+0x70/0xb0
 bus_for_each_dev from bus_add_driver+0x168/0x1f4
 bus_add_driver from driver_register+0x7c/0x118
 driver_register from do_one_initcall+0x44/0x1ec
 do_one_initcall from kernel_init_freeable+0x238/0x288
 kernel_init_freeable from kernel_init+0x18/0x12c
 kernel_init from ret_from_fork+0x14/0x2c
... ...
---[ end trace 0000000000000000 ]---

Therefore, take the same action as in amba_match(): return -EPROBE_DEFER
if dev->periphid is not ready in amba_probe().

Fixes: f2d3b9a46e0e ("ARM: 9220/1: amba: Remove deferred device addition")
Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
KernelVersion: v6.0-rc3
 drivers/amba/bus.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

v1 --> v2:
1. Update this patch based on:
   https://lore.kernel.org/lkml/20220818172852.3548-1-isaacmanjarres@google.com/
2. Move the operations of sanity checking and reading dev->periphid,
   updating uevent into new function amba_prepare_periphid().

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 110a535648d2e1f..8e4c7e190880206 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -204,10 +204,9 @@ static int amba_read_periphid(struct amba_device *dev)
 	return ret;
 }
 
-static int amba_match(struct device *dev, struct device_driver *drv)
+static int amba_prepare_periphid(struct device *dev)
 {
 	struct amba_device *pcdev = to_amba_device(dev);
-	struct amba_driver *pcdrv = to_amba_driver(drv);
 
 	mutex_lock(&pcdev->periphid_lock);
 	if (!pcdev->periphid) {
@@ -228,6 +227,19 @@ static int amba_match(struct device *dev, struct device_driver *drv)
 	}
 	mutex_unlock(&pcdev->periphid_lock);
 
+	return 0;
+}
+
+static int amba_match(struct device *dev, struct device_driver *drv)
+{
+	struct amba_device *pcdev = to_amba_device(dev);
+	struct amba_driver *pcdrv = to_amba_driver(drv);
+	int ret;
+
+	ret = amba_prepare_periphid(dev);
+	if (ret)
+		return ret;
+
 	/* When driver_override is set, only bind to the matching driver */
 	if (pcdev->driver_override)
 		return !strcmp(pcdev->driver_override, drv->name);
@@ -278,9 +290,15 @@ static int amba_probe(struct device *dev)
 {
 	struct amba_device *pcdev = to_amba_device(dev);
 	struct amba_driver *pcdrv = to_amba_driver(dev->driver);
-	const struct amba_id *id = amba_lookup(pcdrv->id_table, pcdev);
+	const struct amba_id *id;
 	int ret;
 
+	ret = amba_prepare_periphid(dev);
+	if (ret)
+		return ret;
+
+	id = amba_lookup(pcdrv->id_table, pcdev);
+
 	do {
 		ret = of_amba_device_decode_irq(pcdev);
 		if (ret)
-- 
2.25.1

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