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Message-ID: <20160308210333.7ad77a29@lxorguk.ukuu.org.uk>
Date: Tue, 8 Mar 2016 21:03:33 +0000
From: One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To: Scott Bauer <sbauer@....utah.edu>
Cc: linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
x86@...nel.org, wmealing@...hat.com, ak@...ux.intel.com,
luto@...capital.net, Abhiram Balasubramanian <abhiram@...utah.edu>
Subject: Re: [PATCH v3 2/3] x86: SROP mitigation: implement signal cookies
> static int ia32_restore_sigcontext(struct pt_regs *regs,
> - struct sigcontext_32 __user *sc)
> + struct sigcontext_32 __user *sc,
> + void __user **user_cookie)
> {
> unsigned int tmpflags, err = 0;
> void __user *buf;
> @@ -105,6 +106,16 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
> buf = compat_ptr(tmp);
> } get_user_catch(err);
>
> + /*
> + * If there is fp state get cookie from the top of the fp state,
> + * else get it from the top of the sig frame.
> + */
> +
> + if (tmp != 0)
> + *user_cookie = compat_ptr(tmp + fpu__getsize(1));
> + else
> + *user_cookie = NULL;
user_cookie is is __user, so shouldn't just be poking at it without
get/put_user ? It might fault if someone has engineered a bad stack frame.
Alan
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