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SubjectRe: [PATCH] omfs: fix memory leak
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On Sun, 2010-07-04 at 07:37 -0400, me@bobcopeland.com wrote:
> On Sat, Jul 03, 2010 at 10:33:48PM -0400, Davidlohr Bueso wrote:
> > Hi,
> >
> > In omfs_fill_super(), when returning on error, sbi is not being freed.
> >
> > Thanks,
> > Davidlohr.
>
> Hi Davidlohr,
>
> I don't think this is right:
>
> fill_super:
> err = omfs_fill_super()
> if (err)
> deactivate_locked_super(sb)
> kill_sb()
> generic_shutdown_super()
> sop->put_super()
> ...
> omfs_put_super()
> kfree(sbi->s_imap);
> kfree(sbi);
>
> So your change would cause a crash at the first kfree in omfs_put_super().
>
> It looks fine to me as-is, or am I missing something?

Thanks for the reply, Bob. Please bare with me, as I am learning about
the VFS workings. To my knowledge this would happen:

a user tries to mount a omfs partition:
omfs_get_sb() -> omfs_fill_super()

If omfs_fill_super() fails, in this case 'ret' being a non 0 value, the
mount will not be completed, hence the previously allocated 'sbi'
variable will not be freed.

Isn't put_super() called to free data when things run "normally", like
for unmounting? So this function does two things:

kfree(sbi->s_imap)
kfree(sbi)

However, in omfs_get_imap() 'sbi->s_imap' is freed upon failure, so
wouldn't this also crash on the first kfree in omfs_put_super()?
Wouldn't this be the same for freeing sbi upon failure in
omfs_fill_super()?

Now, the patch I sent is compile-tested only, so it might crash it. I
will test it properly.

If what I just said is complete nonsense, please enlighten me.

Thanks,
Davidlohr

>
> >
> > Signed-off-by: Davidlohr Bueso <dave@gnu.org>
> > ---
> > fs/omfs/inode.c | 4 +++-
> > 1 files changed, 3 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/omfs/inode.c b/fs/omfs/inode.c
> > index 089839a..253846e 100644
> > --- a/fs/omfs/inode.c
> > +++ b/fs/omfs/inode.c
> > @@ -523,12 +523,14 @@ static int omfs_fill_super(struct super_block *sb, void *data, int silent)
> > }
> > printk(KERN_DEBUG "omfs: Mounted volume %s\n", omfs_rb->r_name);
> >
> > - ret = 0;
> > + ret = 0; /* success */
> > out_brelse_bh2:
> > brelse(bh2);
> > out_brelse_bh:
> > brelse(bh);
> > end:
> > + if (ret != 0)
> > + kfree(sbi);
> > return ret;
> > }
>




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