Messages in this thread Patch in this message |  | | From | Jann Horn <> | Subject | [PATCH] ppdev: fix double-free of pp->pdev->name | Date | Sun, 30 Oct 2016 16:44:08 +0100 |
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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] ==========================================================
CCing Andy Lutomirski because I think this is what broke vmapped stacks for me - after applying this patch, vmapped stacks worked for me. Previously, I got oopses (and lockups) caused by area->pages[0] being 0x400000000 in __vunmap(), with area->pages being allocated in the kmalloc area.
Signed-off-by: Jann Horn <jann@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
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