[PATCH v2] ppdev: fix double-free of pp->pdev->name

[Jann Horn]

free_pardevice() is called by parport_unregister_device() and already frees
pp->pdev->name, don't try to do it again.

This bug causes kernel crashes.

I found and verified this with KASAN and some added pr_emerg()s:

[   60.316568] pp_release: pp->pdev->name == ffff88039cb264c0
[   60.316692] free_pardevice: freeing par_dev->name at ffff88039cb264c0
[   60.316706] pp_release: kfree(ffff88039cb264c0)
[   60.316714] ==========================================================
[   60.316722] BUG: Double free or freeing an invalid pointer
[   60.316731] Unexpected shadow byte: 0xFB
[   60.316801] Object at ffff88039cb264c0, in cache kmalloc-32 size: 32
[   60.316813] Allocated:
[   60.316824] PID = 1695
[   60.316869] Freed:
[   60.316880] PID = 1695
[   60.316935] ==========================================================

Signed-off-by: Jann Horn <j...@thejh.net>
---
 drivers/char/ppdev.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index d23368874710..6af1ce04b3da 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -748,10 +748,7 @@ static int pp_release(struct inode *inode, struct file 
*file)
        }
 
        if (pp->pdev) {
-               const char *name = pp->pdev->name;
-
                parport_unregister_device(pp->pdev);
-               kfree(name);
                pp->pdev = NULL;
                pr_debug(CHRDEV "%x: unregistered pardevice\n", minor);
        }
-- 
2.1.4