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

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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.

> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>

Reviewed-by: David Sterba <dsterba@xxxxxxxx>
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