Re: [PATCH 1/2] vboxsf: Avoid an spurious warning if load_nls_xxx() fails

[Christophe JAILLET]

Le 02/11/2023 à 13:30, Matthew Wilcox a écrit :
> On Wed, Nov 01, 2023 at 11:49:48AM +0100, Christophe JAILLET wrote:
> > If an load_nls_xxx() function fails a few lines above, the 'sbi->bdi_id' is
> > still 0.
> > So, in the error handling path, we will call ida_simple_remove(..., 0)
> > which is not allocated yet.
> >
> > In order to prevent a spurious "ida_free called for id=0 which is not
> > allocated." message, tweak the error handling path and add a new label.
>
> That's not spurious!

My fault, as a non-native English speaking man.
I've always sought that spurious was meaning "odd" or "strange", but I 
was wrong :(

Here, a better wording could be "to prevent an un-expected "ida..."".
Is that ok for you?

Or the last sentence could shortened to only "In order to fix it, tweak 
the error handling path and add a new label.".

CJ

> You're freeing something that wasn't allocated.
> A good quality malloc allocation will warn you if you free() a random
> pointer.  I agree with everything abuot this patch (and the next) except
> for the changelog.
>
> > Fixes: 0fd169576648 ("fs: Add VirtualBox guest shared folder (vboxsf) support")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> >   fs/vboxsf/super.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/vboxsf/super.c b/fs/vboxsf/super.c
> > index 1fb8f4df60cb..9848af78215b 100644
> > --- a/fs/vboxsf/super.c
> > +++ b/fs/vboxsf/super.c
> > @@ -151,7 +151,7 @@ static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
> >   		if (!sbi->nls) {
> >   			vbg_err("vboxsf: Count not load '%s' nls\n", nls_name);
> >   			err = -EINVAL;
> > -			goto fail_free;
> > +			goto fail_destroy_idr;
> >   		}
> >   	}
> >   
> > @@ -224,6 +224,7 @@ static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
> >   		ida_simple_remove(&vboxsf_bdi_ida, sbi->bdi_id);
> >   	if (sbi->nls)
> >   		unload_nls(sbi->nls);
> > +fail_destroy_idr:
> >   	idr_destroy(&sbi->ino_idr);
> >   	kfree(sbi);
> >   	return err;
> > --
> > 2.34.1