AW: [PATCH] jffs2: fix double-free of f->target in jffs2_alloc_inode()

[Richard Weinberger]

Am Sat, Sep 12, 2026, 03:08 schrieb Deepanshu Kartikey <kartikey406@xxxxxxxxx>:

> On Sun, Aug 23, 2026 at 8:57 PM Deepanshu Kartikey
> <kartikey406@xxxxxxxxx> wrote:
> >
> > jffs2_alloc_inode() does not initialize f->target before returning
> > the new inode. It is normally cleared later by
> > jffs2_init_inode_info(), called from jffs2_iget(), but that runs
> > only after alloc_inode() has already returned successfully.
> >
> > If inode_init_always() fails in between, alloc_inode() calls
> > ->free_inode() directly on the half-initialized inode.
> > jffs2_free_inode() then does kfree(f->target) on whatever stale
> > value was left in the reused slab object, which can be a pointer
> > that was already freed, causing a double-free.
> >
> > Initialize f->target to NULL in jffs2_alloc_inode() to close this
> > window, and clear it in jffs2_free_inode() after freeing it so a
> > reused or re-freed object can never carry a dangling pointer.
> >
> > Fixes: 4fdcfab5b553 ("jffs2: fix use-after-free on symlink traversal")
> > Reported-by: syzbot+675e84fdf3dde67b4946@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=675e84fdf3dde67b4946
> > Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>
> > ---
> >  fs/jffs2/super.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
> > index 81396a092ba8..30d753d4c263 100644
> > --- a/fs/jffs2/super.c
> > +++ b/fs/jffs2/super.c
> > @@ -42,6 +42,7 @@ static struct inode *jffs2_alloc_inode(struct super_block *sb)
> >         f = alloc_inode_sb(sb, jffs2_inode_cachep, GFP_KERNEL);
> >         if (!f)
> >                 return NULL;
> > +       f->target = NULL;
> >         return &f->vfs_inode;
> >  }
> >
> > @@ -50,6 +51,7 @@ static void jffs2_free_inode(struct inode *inode)
> >         struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
> >
> >         kfree(f->target);
> > +       f->target = NULL;
> >         kmem_cache_free(jffs2_inode_cachep, f);
> >  }
> >
> > --
> > 2.34.1
> >
> 
> Gentle Reminder. Please let me know the status of this patch.

We got lot's of identical fixes this issue.
I had no time yet to sort out who was the first.
This is maybe the first report with fix suggestions, but the reporter
vanished:
https://lore.kernel.org/linux-mtd/CAFLxGvyZO_EDo-YM_EybZG3u7aNUoNiThhvbhQCrOPD7mPV6GA@xxxxxxxxxxxxxx/

Thanks,
//richard