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From: Kees Cook <>
Subject: Re: [PATCH] ovl: explicitly initialize error in ovl_copy_xattr()
Date: Wed, 3 Jun 2020 13:35:09 -0700
Message-ID: <202006031219.36197D0729@keescook> (raw)
In-Reply-To: <>

On Wed, Jun 03, 2020 at 07:47:14PM +0200, wrote:
> Under certain circumstances (we found this out running Docker on a
> Clang-built kernel with CONFIG_INIT_STACK_ALL) ovl_copy_xattr() may
> return uninitialized value of |error| from ovl_copy_xattr().
> It is then returned by ovl_create() to lookup_open(), which casts it to
> an invalid dentry pointer, that can be further read or written by the
> lookup_open() callers.
> Signed-off-by: Alexander Potapenko <>

Fixes: e4ad29fa0d22 ("ovl: use a minimal buffer in ovl_copy_xattr")
Reviewed-by: Kees Cook <>

It seems the error isn't reported anywhere, so the value likely isn't
too important. -EINVAL seems sane to me.

Thought: should CONFIG_INIT_STACK_ALL=y disable uninitialized_var()?

$ git grep uninitialized_var | wc -l

We have evidence this is being used inappropriately and is masking bugs.
I would actually think it should should be removed globally, but it
seems especially important for CONFIG_INIT_STACK_ALL=y.

I've opened:

Kees Cook

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-03 17:47 glider
2020-06-03 20:35 ` Kees Cook [this message]
2020-06-03 21:46 ` Vivek Goyal
2020-06-04  8:28   ` Alexander Potapenko
2020-06-04  8:42 glider
2020-06-04  8:57 ` Miklos Szeredi
2020-06-04 16:00   ` Kees Cook
2020-06-04 15:57 ` Kees Cook
2020-06-05  9:46   ` Alexander Potapenko
2020-06-05  9:54   ` Miklos Szeredi

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