Fwd: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list instead of free items

[Jincheng Wang]

---------- Forwarded message ---------
发件人： Jincheng Wang <jc.w4ng at gmail.com>
Date: 2021年10月31日周日 下午6:23
Subject: Re: [PATCH1/1]sqfs: sqfs_tokenize() should fill the tokens list
instead of free items
To: Miquel Raynal <miquel.raynal at bootlin.com>


Hello,

Apologize for a late reply ,and I made a mistake in wirting mail.

Here is the email before I commit the patch.

Double free vulnerability in sqfs commands ("sqfsls" and "sqfsload")

On Tue, Oct 12, 2021 at 04:07:43PM +0800, Jincheng Wang wrote:

> Hello U-Boot lists!
> I had been doing a fuzz testing in U-Boot .
> There is a double free bug in U-Boot, in /fs/squashfs/sqfs.c in the
> function sqfs_tokenize( ).
> On the line 307, tokens[i] is being freed and the ret is being set
-ENOMEM,
> it will go to the out: label and free tokens[i] again (just like
> CVE-2020-8432, double free in do_rename_gpt_parts() ).
> Here is  a sample command cause to crash in sandbox environment:
>     host bind 0 test.sqsh
>     sqfsls host 0 1//3

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

The vulnerability can be fixed with a new return value and a new label. But
I didn't want to creat  these, I chose another way.

Regards,
Jincheng


Miquel Raynal <miquel.raynal at bootlin.com> 于2021年10月27日周三 下午4:17写道：

> Hello,
>
> trini at konsulko.com wrote on Tue, 26 Oct 2021 15:25:56 -0400:
>
> > On Sat, Oct 16, 2021 at 10:19:48AM +0800, Jincheng Wang wrote:
> >
> > > We can delete two lines of code to avoid double free bug, but still a
> wild
> > > pointers bug.
> > >
> > > A test for wild pointers:
> > >     sqfsls host 0  1//2/3//4/5
> > >
> > > Fill the tokens list can solve it well.
> > >
> > >
> > > Signed-off-by: Jincheng Wang <jc.w4ng at gmail.com>
> > > ---
> > >  fs/squashfs/sqfs.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > >   }
> > >
> > > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> > > index e2d91c654c..50d3f8b71e 100644
> > > --- a/fs/squashfs/sqfs.c
> > > +++ b/fs/squashfs/sqfs.c
> > > @@ -303,8 +303,9 @@ static int sqfs_tokenize(char **tokens, int count,
> > > const char *str)
> > >   aux = strtok(!j ? strc : NULL, "/");
> > >   tokens[j] = strdup(aux);
> > >   if (!tokens[j]) {
> > > - for (i = 0; i < j; i++)
> > > - free(tokens[i]);
>
> Where is the double free here? Why do you stop freeing the tokens list?
>
> > > + /* fill tokens list to avoid wild pointers being freed*/
> > > + for (i = j + 1; i < count; i++)
> > > + tokens[i] = 0;
>
> This does not feel right. Perhaps it's just me not getting through the
> lack of spacing successfully but this deserves more explanations.
>
> > >   ret = -ENOMEM;
> > >   goto free_strc;
> >
> > Aside from the whitespace having been destroyed, any comments from the
> > maintainers / reviewers?  Thanks!
> >
>
> Thanks,
> Miquèl
>