Re: [PATCH 2/2] mtd: Check add_mtd_device() ret code

[Boris Brezillon <bbrezillon@kernel.org>]

Hi Geert,

On Tue, 22 Jan 2019 13:31:59 +0100
Boris Brezillon <bbrezillon@kernel.org> wrote:

> On Tue, 22 Jan 2019 12:21:11 +0100
> Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> 
> > Hi Boris,
> > 
> > On Wed, Jan 2, 2019 at 3:37 PM Boris Brezillon <bbrezillon@kernel.org> wrote:  
> > > add_mtd_device() can fail. We should always check its return value
> > > and gracefully handle the failure case. Fix the call sites where this
> > > not done (in mtdpart.c) and add a __must_check attribute to the
> > > prototype to avoid this kind of mistakes.
> > >
> > > Signed-off-by: Boris Brezillon <bbrezillon@kernel.org>
> > > ---
> > > No Fixes or Cc-stable tag here, as this seems to have worked just fine
> > > without checking add_mtd_device() ret code until we started to expose
> > > MTD devices as NVMEM providers (queued for 4.21).    
> > 
> > Oh yes ;-)
> > 
> > https://lore.kernel.org/lkml/87feac02-e955-1897-d4a4-d6d6d1082e45@gmail.com/t/
> > 
> > Your patch is very similar to mine, so the crash is gone.  
> 
> Oops, sorry about that. I completely forgot about this patch. It seems
> the discussion led to a different conclusion though (patch
> allocate_partitions() to reject wrong parts early) and the v2 was never
> sent (or I missed it). Anyway, I guess we should have done both (check
> add_mtd_device() ret code everywhere and patch allocate_partitions() to
> reject bad parts early).
> 
> > However, the warning is still there:
> > 
> >     m25p80 spi0.0: s25sl032p (4096 Kbytes)
> >     3 fixed-partitions partitions found on MTD device spi0.0
> >     Creating 3 MTD partitions on "spi0.0":
> >     0x000000000000-0x000000080000 : "loader"
> >     0x000000080000-0x000000600000 : "user"
> >     mtd: partition "user" extends beyond the end of device "spi0.0" --
> > size truncated to 0x380000
> >     0x000000600000-0x000004000000 : "flash"
> >     mtd: partition "flash" is out of reach -- disabled
> >     ------------[ cut here ]------------
> >     WARNING: CPU: 0 PID: 1 at drivers/mtd/mtdcore.c:571
> > add_mtd_device+0x90/0x3b0
> > 
> > Interestingly, only one partition is created, covering the full size of the
> > device:
> > 
> >     # cat /proc/partitions
> >     major minor  #blocks  name
> > 
> >       31        0       4096 mtdblock0
> > 
> > While I would expect two partitions, "loader" and truncated "user":
> > 
> >       31        0        512 mtdblock0
> >       31        1       3584 mtdblock1  
> 
> Yes, makes sense, I guess your patch was better than mine :-/. Can you
> try with the following diff applied and let me know if it solves the
> problem?

Gentle ping: is this diff fixing your problem, and do you want me to
send a proper patch for it or should I let you send one?

> 
> --->8---  
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index 60104e1079c5..aefd3344991f 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -724,16 +724,14 @@ int add_mtd_partitions(struct mtd_info *master,
>  {
>         struct mtd_part *slave;
>         uint64_t cur_offset = 0;
> -       int i, ret;
> +       int i, ret, actual_nbparts = 0;
>  
>         printk(KERN_NOTICE "Creating %d MTD partitions on \"%s\":\n", nbparts, master->name);
>  
>         for (i = 0; i < nbparts; i++) {
>                 slave = allocate_partition(master, parts + i, i, cur_offset);
> -               if (IS_ERR(slave)) {
> -                       ret = PTR_ERR(slave);
> -                       goto err_del_partitions;
> -               }
> +               if (IS_ERR(slave))
> +                       continue;
>  
>                 mutex_lock(&mtd_partitions_mutex);
>                 list_add(&slave->list, &mtd_partitions);
> @@ -746,7 +744,7 @@ int add_mtd_partitions(struct mtd_info *master,
>                         mutex_unlock(&mtd_partitions_mutex);
>  
>                         free_partition(slave);
> -                       goto err_del_partitions;
> +                       continue;
>                 }
>  
>                 mtd_add_partition_attrs(slave);
> @@ -754,14 +752,10 @@ int add_mtd_partitions(struct mtd_info *master,
>                 parse_mtd_partitions(&slave->mtd, parts[i].types, NULL);
>  
>                 cur_offset = slave->offset + slave->mtd.size;
> +               actual_nbparts++;
>         }
>  
> -       return 0;
> -
> -err_del_partitions:
> -       del_mtd_partitions(master);
> -
> -       return ret;
> +       return actual_nbparts;
>  }
>  
>  static DEFINE_SPINLOCK(part_parser_lock);
> @@ -1003,10 +997,10 @@ int parse_mtd_partitions(struct mtd_info *master, const char *const *types,
>                 }
>                 /* Found partitions! */
>                 if (ret > 0) {
> -                       err = add_mtd_partitions(master, pparts.parts,
> +                       ret = add_mtd_partitions(master, pparts.parts,
>                                                  pparts.nr_parts);
>                         mtd_part_parser_cleanup(&pparts);
> -                       return err ? err : pparts.nr_parts;
> +                       return ret;
>                 }
>                 /*
>                  * Stash the first error we see; only report it if no parser


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