[Bug 216454] New: scsi: megaraid_sas: possible use-after-free caused by bad error handling in megasas_probe_one()

[bugzilla-daemon@xxxxxxxxxx]

https://bugzilla.kernel.org/show_bug.cgi?id=216454

            Bug ID: 216454
           Summary: scsi: megaraid_sas: possible use-after-free caused by
                    bad error handling in megasas_probe_one()
           Product: IO/Storage
           Version: 2.5
    Kernel Version: 5.10.0
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: SCSI
          Assignee: linux-scsi@xxxxxxxxxxxxxxx
          Reporter: r33s3n6@xxxxxxxxx
        Regression: No

Hello,

Our fault injection tool finds a possible use-after-free in the 
megaraid_sas driver in Linux 5.10.0:

In the file drivers/scsi/megaraid/megaraid_sas_base.c:
In megasas_io_attach(), the call to scsi_add_host() may fail: 
6814:   if (scsi_add_host(host, &instance->pdev->dev)) {
            ...
6818:           return -ENODEV;
6819:   }

This error is then propagated to its caller megasas_probe_one().
7414:   if (megasas_io_attach(instance))
7415:           goto fail_io_attach;

In error handling code of megasas_probe_one(), it calls scsi_host_put():
7457:   scsi_host_put(host);

The function scsi_host_put() calls scsi_host_dev_release() to free `host`,
which contains a variable `instance`.

But megasas_probe_one() calls megasas_init_fw() before:
7372:   if (megasas_init_fw(instance))

In megasas_init_fw(), it starts a timer:
6369:   megasas_start_timer(instance);

And megasas_probe_one() does nothing about it in error handling code. When
the timer expires, it accesses `instance`, causing a use-after-free bug.

I am not quite sure how to fix this possible bug. Any feedback would be
appreciated, thanks!

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>

Best wishes,
Zixuan Fu

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