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    Subject[PATCH 5.0 115/238] intel_th: Dont reference unassigned outputs
    Date
    5.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

    commit 9ed3f22223c33347ed963e7c7019cf2956dd4e37 upstream.

    When an output port driver is removed, also remove references to it from
    any masters. Failing to do this causes a NULL ptr dereference when
    configuring another output port:

    > BUG: unable to handle kernel NULL pointer dereference at 000000000000000d
    > RIP: 0010:master_attr_store+0x9d/0x160 [intel_th_gth]
    > Call Trace:
    > dev_attr_store+0x1b/0x30
    > sysfs_kf_write+0x3c/0x50
    > kernfs_fop_write+0x125/0x1a0
    > __vfs_write+0x3a/0x190
    > ? __vfs_write+0x5/0x190
    > ? _cond_resched+0x1a/0x50
    > ? rcu_all_qs+0x5/0xb0
    > ? __vfs_write+0x5/0x190
    > vfs_write+0xb8/0x1b0
    > ksys_write+0x55/0xc0
    > __x64_sys_write+0x1a/0x20
    > do_syscall_64+0x5a/0x140
    > entry_SYSCALL_64_after_hwframe+0x44/0xa9

    Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Fixes: b27a6a3f97b9 ("intel_th: Add Global Trace Hub driver")
    CC: stable@vger.kernel.org # v4.4+
    Reported-by: Ammy Yi <ammy.yi@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/hwtracing/intel_th/gth.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/drivers/hwtracing/intel_th/gth.c
    +++ b/drivers/hwtracing/intel_th/gth.c
    @@ -607,6 +607,7 @@ static void intel_th_gth_unassign(struct
    {
    struct gth_device *gth = dev_get_drvdata(&thdev->dev);
    int port = othdev->output.port;
    + int master;

    if (thdev->host_mode)
    return;
    @@ -615,6 +616,9 @@ static void intel_th_gth_unassign(struct
    othdev->output.port = -1;
    othdev->output.active = false;
    gth->output[port].output = NULL;
    + for (master = 0; master < TH_CONFIGURABLE_MASTERS; master++)
    + if (gth->master[master] == port)
    + gth->master[master] = -1;
    spin_unlock(&gth->gth_lock);
    }


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