Re: [PATCH] UBI: Fix crash in try_recover_peb()

[Geert Uytterhoeven]

Hi Boris,

On Thu, Oct 13, 2016 at 4:24 PM, Boris Brezillon
<boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 13 Oct 2016 16:05:36 +0200
> Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>
>>     drivers/mtd/ubi/eba.c: In function âtry_recover_pebâ:
>>     drivers/mtd/ubi/eba.c:744: warning: âvid_hdrâ is used uninitialized in this function
>>
>> The pointer vid_hdr is indeed not initialized, leading to a crash when
>> it is dereferenced.
>>
>> Fix this by obtaining the pointer from the VID buffer, like is done
>> everywhere else.
>
> Indeed, I don't know how I missed that one :-/.
>
>>
>> Fixes: 3291b52f9ff0acc8 ("UBI: introduce the VID buffer concept")
>> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>
> One minor comment below, otherwise
>
> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>

Thanks!

>> ---
>> Completely untested. And I know nothing about UBI ;-)
>> ---
>>  drivers/mtd/ubi/eba.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
>> index 95c4048a371e87b6..388e46be6ad92805 100644
>> --- a/drivers/mtd/ubi/eba.c
>> +++ b/drivers/mtd/ubi/eba.c
>> @@ -741,6 +741,7 @@ static int try_recover_peb(struct ubi_volume *vol, int pnum, int lnum,
>>               goto out_put;
>>       }
>>
>> +     vid_hdr = ubi_get_vid_hdr(vidb);
>
> Can you move this assignment at variable declaration time?

I can do that. However, that moves the call to ubi_get_vid_hdr() _before_
the call to ubi_io_read_vid_hdr().

While that would still work (ubi_get_vid_hdr() would just return a pointer to
the not-yet-read data), I think it's better to not move it, to prevent people
from accidentally trying to use it before the data has been read.

Do you agree?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds