Re: [PATCH] scsi: libsas: fix error handling in sas_phy_add()

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Hi,

On 2022/11/7 17:35, John Garry wrote:
On 05/11/2022 07:17, Yang Yingliang wrote:

This is not libsas.

BTW, before I go further, note this:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst#n312
Thanks for replying.

Yes, it should be "scsi: scsi_transport_sas: XXX"

If transport_add_device() fails in sas_phy_add(), but it's not handled,
it will lead kernel crash because of trying to delete not added device
in transport_remove_device() called from sas_remove_host().

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000108 CPU: 61 PID: 42829 Comm: rmmod Kdump: loaded Tainted: G W          6.1.0-rc1+ #173
pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : device_del+0x54/0x3d0
lr : device_del+0x37c/0x3d0
Call trace:
  device_del+0x54/0x3d0
  attribute_container_class_device_del+0x28/0x38
  transport_remove_classdev+0x6c/0x80
  attribute_container_device_trigger+0x108/0x110
  transport_remove_device+0x28/0x38
  sas_phy_delete+0x30/0x60 [scsi_transport_sas]
  do_sas_phy_delete+0x6c/0x80 [scsi_transport_sas]
  device_for_each_child+0x68/0xb0
  sas_remove_children+0x40/0x50 [scsi_transport_sas]
  sas_remove_host+0x20/0x38 [scsi_transport_sas]
  hisi_sas_remove+0x40/0x68 [hisi_sas_main]
  hisi_sas_v2_remove+0x20/0x30 [hisi_sas_v2_hw]
  platform_remove+0x2c/0x60

Fix this by checking and handling return value of transport_add_device()
in sas_phy_add(). transport_destroy_device() has been called in sas_phy_free()
in the error path, so it's no need to call it here.

"there's no need", rather than "it's no need". And I don't know why you bother even mentioning about transport_destroy_device().

Because the device set up by transport_setup_device(), it should be destroyed by transport_destroy_device(), so I mention this.



Fixes: c7ebbbce366c ("[SCSI] SAS transport class")
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
  drivers/scsi/scsi_transport_sas.c | 7 +++++--
  1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 2f88c61216ee..cb364a7c6097 100644
--- a/drivers/scsi/scsi_transport_sas.c
+++ b/drivers/scsi/scsi_transport_sas.c
@@ -723,8 +723,11 @@ int sas_phy_add(struct sas_phy *phy)
        error = device_add(&phy->dev);
      if (!error) {

personally I think that the following looks better:

int sas_phy_add(struct sas_phy *phy)
{
    int error;

    error = device_add(&phy->dev);
    if (error)
        return error;

    error = transport_add_device(&phy->dev);
    if (error) {
        device_del(&phy->dev);
        return error;
    }
    transport_configure_device(&phy->dev);

    return 0;
}
EXPORT_SYMBOL(sas_phy_add);
Yes, it's looks better, but I was trying to change least this code to fix this problem.
I can send a v2 later to change these.

Thanks,
Yang

- transport_add_device(&phy->dev);
-        transport_configure_device(&phy->dev);
+        error = transport_add_device(&phy->dev);
+        if (!error)
+            transport_configure_device(&phy->dev);
+        else
+            device_del(&phy->dev);
      }
        return error;


.



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