Thanks David

There is definitely a problem if you unlink a symlink.

I am a bit concerned about the apporach you propose because I don't like the 
idea of using the object after it has been deleted.

Instead I propose to do something like:
static int yaffs_DeleteSymLink(yaffs_Object * in)
{
         YFREE(in->variant.symLinkVariant.alias);
+      in->variant.symLinkVariant = NULL;
        return yaffs_DoGenericObjectDeletion(in);
}

then handling a NULL value properly where need be.

-- Charles

On Wednesday 02 December 2009 12:58:52 Charles Manning wrote:
> What do you mean by "no longer mountable"?
>
> I'll take a look at your analysis to see what's going on.
>
> -- Charles
>
> On Wednesday 02 December 2009 11:33:52 Chris David wrote:
> > Hello,
> >
> > I've been trying to figure out why sometimes our NAND device becomes
> > corrupt and is no longer mountable.  The symptom appears to be that in
> > the yaffs_ScanBackwards function, around line 6719 in yaffs_guts.c,
> > under the YAFFS_OBJECT_TYPE_SYMLINK case, there is a call:
> > yaffs_CloneString(oh->alias), and this is returning an empty string.
> > How could this happen?  Well, I have a possible explanation and a
> > patch.
> >
> > diff -u build_mipsel/linux-2.6.23-msp2/fs/yaffs2/yaffs_guts.c.orig
> > build_mipsel/linux-2.6.23-msp2/fs/yaffs2/yaffs_guts.c ---
> > build_mipsel/linux-2.6.23-msp2/fs/yaffs2/yaffs_guts.c.orig  2009-12-01
> > 14:41:27.000000000 -0800 +++
> > build_mipsel/linux-2.6.23-msp2/fs/yaffs2/yaffs_guts.c       2009-12-01
> > 14:42:21.000000000 -0800 @@ -5157,9 +5157,10 @@
> >
> >  static int yaffs_DeleteSymLink(yaffs_Object * in)
> >  {
> > +       int retv;
> > +       retv = yaffs_DoGenericObjectDeletion(in);
> >         YFREE(in->variant.symLinkVariant.alias);
> > -
> > -       return yaffs_DoGenericObjectDeletion(in);
> > +       return retv;
> >  }
> >
> >  static int yaffs_DeleteHardLink(yaffs_Object * in)
> >
> > I observed the following by analyzing the code.  There could be a call
> > stack as follows:
> >
> > yaffs_DeleteSymLink(yaffs_Object * in)
> > yaffs_DoGenericObjectDeletion(in)
> > yaffs_ChangeObjectName(in, ...
> > yaffs_UpdateObjectHeader(obj, ...
> >
> > which gets to about line 3806 (still yaffs_guts.c), where there is:
> > yaffs_strncpy(oh->alias,
> >   in->variant.symLinkVariant.alias,
> >   YAFFS_MAX_ALIAS_LENGTH);
> >
> > well, in->variant.symLinkVariant.alias is already freed at this point.
> > The above patch would fix this.
> >
> > I am not 100% confident in my findings.  Does anyone agree that this
> > could be a real bug?  I was thinking that if
> > in->myDev->deletedDir->variantType is set to something other than
> > YAFFS_OBJECT_TYPE_DIRECTORY, perhaps it isn't.
> >
> > Thanks,
> >
> > -Chris
> >
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > yaffs mailing list
> > yaffs@lists.aleph1.co.uk
> > http://lists.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs
>
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