[PATCH] fs: squasfs: fix a possible NULL pointer dereference in sqfs_opendir()

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Richard,

Richard Genoud <richard.genoud@posteo.net> wrote on Mon, 21 Dec 2020
16:26:00 +0100:

> Le 21/12/2020 ? 16:14, Miquel Raynal a ?crit?:
> > Hi Richard,
> > 
> > Richard Genoud <richard.genoud@posteo.net> wrote on Mon, 21 Dec 2020
> > 16:06:37 +0100:
> >   
> >> Hi Miquel,
> >>
> >> Le 18/12/2020 ? 19:50, Miquel Raynal a ?crit?:  
> >>> Hi Richard,
> >>>
> >>> Richard Genoud <richard.genoud@posteo.net> wrote on Fri, 18 Dec 2020
> >>> 15:24:40 +0100:  
> >>>    >>>> token_count may be != 0 and token_list not yet allocated when the out  
> >>>> code is reached  
> >>>
> >>> Wouldn't it be better to initialize token_count than adding an
> >>> (obscure) indentation level?  
> >> Well, token_count is initialized :
> >> token_count = sqfs_count_tokens(filename);
> >>
> >> But token_list is not yet populated. It is some lines bellow:
> >> token_list = malloc(token_count * sizeof(char *));
> >>
> >>
> >> But I could use something like that, maybe it's clearer :
> >> 	for (j = 0; (token_list != NULL) && (j < token_count); j++)
> >> 		free(token_list[j]);  
> > 
> > I had a look at the code, the error path is clearly not correctly
> > organized.
> > 
> > I think the right approach would be to have real labels like,
> > free_token_list, free_this, free_that and for each of them only do the
> > right cleanup. Doing so should fix the issue.  
> 
> So you're suggesting to revert this ?
> commit ea1b1651c6a8 ("fs/squashfs: sqfs_opendir: simplify error handling")

Yes (our e-mails crossed each other), I think it's best to have a well
organized error path. Of course this error path is maybe faulty, in
this case it must be fixed. But I personally prefer the revert + fix
approach.

Thanks,
Miqu?l