Re: [PATCH] btrfs: ioctl: Fix memory leak on duplicated memory

[David Sterba <dsterba@suse.cz>]

On Thu, Sep 25, 2025 at 10:25:29AM -0700, Boris Burkov wrote:
> On Thu, Sep 25, 2025 at 04:53:31PM +0200, Miquel Sabaté Solà wrote:
> > On 'btrfs_ioctl_qgroup_assign' we first duplicate the argument as
> > provided by the user, which is kfree'd in the end. But this was not the
> > case when allocating memory for 'prealloc'. In this case, if it somehow
> > failed, then the previous code would go directly into calling
> > 'mnt_drop_write_file', without freeing the string duplicated from the
> > user space.
> > 
> > Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
> 
> LGTM, thanks for the fix!
> 
> One thing though: I don't like the label names. I think with multiple
> cleanups the best way is to name each label with the cleanup it is for.
> Once you have some named ones, "out" feels unspecific, and encoding
> every single action like "out_sa_drop_write" doesn't scale as you add
> more cleanups, so it's just not a useful pattern. It's already quite
> clunky with just two.

The patch is adding a new label and it follows the pattern we use
elsewhere, with "out_<what>" pattern. The standalone 'out' is there and
I agree it should be named like 'out_free_prealloc' or such but it's in
the original code and it's been there for a long time. Cleaning that up
is for another patch.