linux-kernel - Re: [PATCH] binfmt_flat: Fix integer overflow bug on 32 bit systems

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Message-ID: <4252467r-08n8-4oqr-3910-p5n1pq8so9s5@onlyvoer.pbz>
Date: Fri, 10 Jan 2025 10:55:25 -0500 (EST)
From: Nicolas Pitre <npitre@...libre.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
cc: Alexander Viro <viro@...iv.linux.org.uk>, 
    Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
    Kees Cook <kees@...nel.org>, Eric Biederman <ebiederm@...ssion.com>, 
    linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, 
    linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] binfmt_flat: Fix integer overflow bug on 32 bit
 systems

On Fri, 10 Jan 2025, Dan Carpenter wrote:

> Ping.
> 
> regards,
> dan carpenter
> 
> On Wed, Dec 04, 2024 at 03:07:15PM +0300, Dan Carpenter wrote:
> > Most of these sizes and counts are capped at 256MB so the math doesn't
> > result in an integer overflow.  The "relocs" count needs to be checked
> > as well.  Otherwise on 32bit systems the calculation of "full_data"
> > could be wrong.
> > 
> > 	full_data = data_len + relocs * sizeof(unsigned long);
> > 
> > Fixes: c995ee28d29d ("binfmt_flat: prevent kernel dammage from corrupted executable headers")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

Acked-by: Nicolas Pitre <npitre@...libre.com>


> > ---
> >  fs/binfmt_flat.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
> > index 390808ce935d..b5b5ca1a44f7 100644
> > --- a/fs/binfmt_flat.c
> > +++ b/fs/binfmt_flat.c
> > @@ -478,7 +478,7 @@ static int load_flat_file(struct linux_binprm *bprm,
> >  	 * 28 bits (256 MB) is way more than reasonable in this case.
> >  	 * If some top bits are set we have probable binary corruption.
> >  	*/
> > -	if ((text_len | data_len | bss_len | stack_len | full_data) >> 28) {
> > +	if ((text_len | data_len | bss_len | stack_len | relocs | full_data) >> 28) {
> >  		pr_err("bad header\n");
> >  		ret = -ENOEXEC;
> >  		goto err;
> > -- 
> > 2.45.2
>