From: Kees Cook Date: Tue, 30 Jul 2019 17:11:19 +0000 Subject: Re: [PATCH] randstruct: fix a bug in is_pure_ops_struct() Message-Id: <201907301008.622218EE5@keescook> List-Id: References: <20190727155841.GA13586@host> In-Reply-To: <20190727155841.GA13586@host> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Joonwon Kang Cc: re.emese@gmail.com, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org On Sun, Jul 28, 2019 at 12:58:41AM +0900, Joonwon Kang wrote: > Before this, there were false negatives in the case where a struct > contains other structs which contain only function pointers because > of unreachable code in is_pure_ops_struct(). Ah, very true. Something like: struct internal { void (*callback)(void); }; struct wrapper { struct internal foo; void (*other_callback)(void); }; would have not been detected as is_pure_ops_struct()? How did you notice this? (Are there cases of this in the kernel?) > Signed-off-by: Joonwon Kang Applied; thanks! -Kees > --- > scripts/gcc-plugins/randomize_layout_plugin.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c > index 6d5bbd31db7f..a123282a4fcd 100644 > --- a/scripts/gcc-plugins/randomize_layout_plugin.c > +++ b/scripts/gcc-plugins/randomize_layout_plugin.c > @@ -443,13 +443,12 @@ static int is_pure_ops_struct(const_tree node) > if (node = fieldtype) > continue; > > - if (!is_fptr(fieldtype)) > - return 0; > - > - if (code != RECORD_TYPE && code != UNION_TYPE) > - continue; > + if (code = RECORD_TYPE || code = UNION_TYPE) { > + if (!is_pure_ops_struct(fieldtype)) > + return 0; > + } > > - if (!is_pure_ops_struct(fieldtype)) > + if (!is_fptr(fieldtype)) > return 0; > } > > -- > 2.17.1 > -- Kees Cook