From: Jann Horn <jann@thejh.net>
Date: Sun, 30 Oct 2016 22:19:24 +0000 (+0100)
Subject: ppdev: fix double-free of pp->pdev->name
X-Git-Tag: v4.13~1920^2
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;ds=sidebyside;h=b13d14339baaaa720e7e5448855f33ba501917aa;p=mirror_ubuntu-bionic-kernel.git

ppdev: fix double-free of pp->pdev->name

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 <jann@thejh.net>
Acked-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

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);
 	}