lkml.org 
[lkml]   [2020]   [Jan]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] fs: pstore: fix double-free on ramoops_init_przs
Hello Kees!

It's a pleasure to hear from you!

On 2020-01-07 21:05, Kees Cook wrote:
>
> I think this is a false positive (have you actually hit the
> double-free?). The logic in this area is:

No I did not actually hit the double-free. I'm just following
the indicators from static analyzer.

> nothing was freeing the label on the failed prz, but all the other prz
> labels were free (i.e. there is a "i--" that skips the failed prz
> alloc).

I have noticed that. Thanks for clearing it up though.

The `kfree` I was referring to is in `err:` label of function
`persistent_ram_new` in `ram_core.c#595` of `for-next/pstore` tree:

https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/tree/fs/pstore/ram_core.c?h=for-next/pstore#n595

Here are the relevant bits:

```
struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t
size,
u32 sig, struct persistent_ram_ecc_info *ecc_info,
unsigned int memtype, u32 flags, char *label)
{
/* ... */
/* ... */
/* ... */
return prz;
err:
persistent_ram_free(prz); /* <----- */
return ERR_PTR(ret);
}
```

So, to my understanding, if our `persistent_ram_new` call in `ram.c#583`
fails, it already does clean up the `label` pointer in itself and
returns
an ERR_PTR back to us and our skipping logic does its job.

I might be missing something but it seems so.

Thank you for looking into this.

--
Cengiz Can
@cengiz_io

\
 
 \ /
  Last update: 2020-01-07 20:42    [W:0.056 / U:17.488 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site