[PATCH] firmware: arm_scpi: Fix error handle when scpi probe failed

[huhai]

From: huhai <huhai at kylinos.cn>

When scpi probe fails, do not just return the error code, but also reset
the global scpi_info to NULL, otherwise scpi_hwmon_probe() may get a UAF
and cause panic:

  scpi_protocol FTSC0001:00: incorrect or no SCP firmware found
  ... ...
  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
  Mem abort info:
    ESR = 0x86000005
    Exception class = IABT (current EL), IL = 32 bits
    SET = 0, FnV = 0
    EA = 0, S1PTW = 0
  user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
  [0000000000000000] pgd=0000000000000000, pud=0000000000000000
  Internal error: Oops: 86000005 [#1] SMP
  ... ...
  pc :           (null)
  lr : scpi_hwmon_probe+0x2c/0x4bc [scpi_hwmon]
  sp : ffff801fa13cfb20
  x29: ffff801fa13cfb20 x28: ffff00000931c1e8
  x27: ffff0000093b7318 x26: 000000000000000d
  x25: ffff801fa1174da8 x24: 0000000000000000
  x23: ffff801fa15e9000 x22: 0000000000000000
  x21: ffff0000012c0028 x20: ffff801fa15e9010
  x19: 0000000000000000 x18: 0000000000000000
  x17: 0000000000000000 x16: 0000000000000000
  x15: 0000000000000400 x14: 0000000000000400
  x13: 0000000000000001 x12: 0000000000000018
  x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f
  x9 : fefefefeff2f2f39 x8 : 7f7f7f7f7f7f7f7f
  x7 : 302f2f2f52525345 x6 : ffff801fa5771a8c
  x5 : 0000000000000000 x4 : 0000000000000000
  x3 : ffff801fa13bbc00 x2 : ffff000009360118
  x1 : 0000000000000000 x0 : ffff801fa13cfbbe
  Call trace:
             (null)
   platform_drv_probe+0x50/0xa0
   really_probe+0x240/0x420
   driver_probe_device+0x68/0x134
   __device_attach_driver+0xb8/0x130
   bus_for_each_drv+0x64/0xa0
   __device_attach+0xa8/0x194
   device_initial_probe+0x10/0x1c
   bus_probe_device+0x90/0xa0
   deferred_probe_work_func+0x90/0xe0
   process_one_work+0x1c0/0x390
   worker_thread+0x6c/0x384
   kthread+0xfc/0x12c
   ret_from_fork+0x10/0x18
  Code: bad PC value
  ---[ end trace b4b2f27a69b5712c ]---

Reported-by: k2ci <kernel-bot at kylinos.cn>
Signed-off-by: huhai <huhai at kylinos.cn>
---
 drivers/firmware/arm_scpi.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/firmware/arm_scpi.c b/drivers/firmware/arm_scpi.c
index ddf0b9ff9e15..ad2355814bdf 100644
--- a/drivers/firmware/arm_scpi.c
+++ b/drivers/firmware/arm_scpi.c
@@ -924,17 +924,20 @@ static int scpi_probe(struct platform_device *pdev)
 	count = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
 	if (count < 0) {
 		dev_err(dev, "no mboxes property in '%pOF'\n", np);
-		return -ENODEV;
+		ret = -ENODEV;
+		goto err;
 	}
 
 	scpi_info->channels = devm_kcalloc(dev, count, sizeof(struct scpi_chan),
 					   GFP_KERNEL);
-	if (!scpi_info->channels)
-		return -ENOMEM;
+	if (!scpi_info->channels) {
+		ret = -ENOMEM;
+		goto err;
+	}
 
 	ret = devm_add_action(dev, scpi_free_channels, scpi_info);
 	if (ret)
-		return ret;
+		goto err;
 
 	for (; scpi_info->num_chans < count; scpi_info->num_chans++) {
 		resource_size_t size;
@@ -943,21 +946,24 @@ static int scpi_probe(struct platform_device *pdev)
 		struct mbox_client *cl = &pchan->cl;
 		struct device_node *shmem = of_parse_phandle(np, "shmem", idx);
 
-		if (!of_match_node(shmem_of_match, shmem))
-			return -ENXIO;
+		if (!of_match_node(shmem_of_match, shmem)) {
+			ret = -ENXIO;
+			goto err;
+		}
 
 		ret = of_address_to_resource(shmem, 0, &res);
 		of_node_put(shmem);
 		if (ret) {
 			dev_err(dev, "failed to get SCPI payload mem resource\n");
-			return ret;
+			goto err;
 		}
 
 		size = resource_size(&res);
 		pchan->rx_payload = devm_ioremap(dev, res.start, size);
 		if (!pchan->rx_payload) {
 			dev_err(dev, "failed to ioremap SCPI payload\n");
-			return -EADDRNOTAVAIL;
+			ret = -EADDRNOTAVAIL;
+			goto err;
 		}
 		pchan->tx_payload = pchan->rx_payload + (size >> 1);
 
@@ -983,7 +989,7 @@ static int scpi_probe(struct platform_device *pdev)
 				dev_err(dev, "failed to get channel%d err %d\n",
 					idx, ret);
 		}
-		return ret;
+		goto err;
 	}
 
 	scpi_info->commands = scpi_std_commands;
@@ -1004,7 +1010,7 @@ static int scpi_probe(struct platform_device *pdev)
 	ret = scpi_init_versions(scpi_info);
 	if (ret) {
 		dev_err(dev, "incorrect or no SCP firmware found\n");
-		return ret;
+		goto err;
 	}
 
 	if (scpi_info->is_legacy && !scpi_info->protocol_version &&
@@ -1024,7 +1030,15 @@ static int scpi_probe(struct platform_device *pdev)
 				   scpi_info->firmware_version));
 	scpi_info->scpi_ops = &scpi_ops;
 
-	return devm_of_platform_populate(dev);
+	ret = devm_of_platform_populate(dev);
+	if (ret)
+		goto err;
+
+	return ret;
+err:
+	/* stop exporting SCPI ops through get_scpi_ops */
+	scpi_info = NULL;
+	return ret;
 }
 
 static const struct of_device_id scpi_of_match[] = {
-- 
2.27.0