Re: [PATCH] btrfs: Prevent possible ERR_PTR() dereference

[Nikolay Borisov <nborisov@suse.com>]

On 11.07.2017 20:24, David Sterba wrote:
> On Tue, Jul 11, 2017 at 04:55:51PM +0300, Nikolay Borisov wrote:
>> In btrfs_full_stripe_len/btrfs_is_parity_mirror we have similar code which
>> gets the chunk map for a particular range via get_chunk_map. However,
>> get_chunk_map can return an ERR_PTR value and while the 2 callers do catch
>> this with a WARN_ON they then proceed to indiscriminately dereference the
>> extent map. This of course leads to a crash. Fix the offenders by making the
>> dereference conditional on IS_ERR.
> 
> While the code makes it better, the whole callchain should be fixed. The
> WARN_ON used to be a BUG_ON and the error handling was absent, and still
> is. Although it's unlikely to see the warnings from that, I'd rather see
> it fixed properly. The direct caller of btrfs_full_stripe_len will be
> able to handle it.

What should be returned in case we can't find the chunk_map -EINVAL ?
> 
>> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> 
> Reviewed-by: David Sterba <dsterba@suse.com>
>