Re: [PATCH] Fix memory leak in vc_resize/vc_allocate

From: Catalin Marinas
Date: Tue Aug 15 2006 - 04:14:46 EST

On 14/08/06, Andrew Morton <akpm@xxxxxxxx> wrote:
On Thu, 10 Aug 2006 15:22:21 +0100
Catalin Marinas <catalin.marinas@xxxxxxx> wrote:
> diff --git a/drivers/char/vt.c b/drivers/char/vt.c
> index da7e66a..31c8b32 100644
> --- a/drivers/char/vt.c
> +++ b/drivers/char/vt.c
> @@ -730,7 +730,8 @@ int vc_allocate(unsigned int currcons) /
> visual_init(vc, currcons, 1);
> if (!*vc->vc_uni_pagedir_loc)
> con_set_default_unimap(vc);
> - vc->vc_screenbuf = kmalloc(vc->vc_screenbuf_size, GFP_KERNEL);
> + if (!vc->vc_kmalloced)
> + vc->vc_screenbuf = kmalloc(vc->vc_screenbuf_size, GFP_KERNEL);
> if (!vc->vc_screenbuf) {
> kfree(vc);
> vc_cons[currcons].d = NULL;

hm. Maybe. I'd worry that the memory at vc->vc_screenbuf isn't of the
correct size and this patch will convert a leak into a buffer overrun.

My initial attempt was to free the kmalloc'ed buffer and reallocate it
in vc_allocate (similar to the code in vc_resize) but I realised that
vc_screenbuf kmalloced block is always of the vs_screenbuf_size

Also, what's up with this, in vc_resize()?

if (vc->vc_kmalloced)
vc->vc_screenbuf = newscreen;
vc->vc_kmalloced = 1;

if vc->vc_kmalloced means "there is kmalloced memory at vc->vc_screenbuf"
then this is wrong.

I think the above should be fine because vc_resize can be called
either via vc_allocate->visual_init->fbcon_init when the buffer was
not yet allocated or via a tty ioctl etc. and it needs to free the old

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