From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, linux-arch@vger.kernel.org,
Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Mark Rutland <mark.rutland@arm.com>,
Keno Fischer <keno@juliacomputing.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org,
Gabriel Krisman Bertazi <krisman@collabora.com>
Subject: Re: [patch V4 10/15] x86/entry: Use generic syscall entry function
Date: Tue, 21 Jul 2020 14:47:17 -0700 [thread overview]
Message-ID: <202007211440.BEF76E2@keescook> (raw)
In-Reply-To: <20200721110809.325060396@linutronix.de>
On Tue, Jul 21, 2020 at 12:57:16PM +0200, Thomas Gleixner wrote:
> Replace the syscall entry work handling with the generic version. Provide
> the necessary helper inlines to handle the real architecture specific
> parts, e.g. ptrace.
>
> Use a temporary define for idtentry_enter_user which will be cleaned up
> seperately.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Though, notes and a comment below...
> +/* Check that the stack and regs on entry from user mode are sane. */
> +static __always_inline void arch_check_user_regs(struct pt_regs *regs)
> +{
> + if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
> + /*
> + * Make sure that the entry code gave us a sensible EFLAGS
> + * register. Native because we want to check the actual CPU
> + * state, not the interrupt state as imagined by Xen.
> + */
> + unsigned long flags = native_save_fl();
> + WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF |
> + X86_EFLAGS_NT));
push, pop, bit test
> +
> + /* We think we came from user mode. Make sure pt_regs agrees. */
> + WARN_ON_ONCE(!user_mode(regs));
memory deref, bit test
> +
> + /*
> + * All entries from user mode (except #DF) should be on the
> + * normal thread stack and should have user pt_regs in the
> + * correct location.
> + */
> + WARN_ON_ONCE(!on_thread_stack());
per-cpu deref, subtract, test
> + WARN_ON_ONCE(regs != task_pt_regs(current));
memory deref, test
> + }
> +}
This doesn't look very expensive, and they certain indicate really bad
conditions. Does this need to be behind a CONFIG? (Whatever the answer,
we can probably make those changes in a later series -- some of these
also look not arch-specific...)
--
Kees Cook
next prev parent reply other threads:[~2020-07-21 21:47 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 10:57 [patch V4 00/15] entry, x86, kvm: Generic entry/exit functionality for host and guest Thomas Gleixner
2020-07-21 10:57 ` [patch V4 01/15] seccomp: Provide stub for __secure_computing() Thomas Gleixner
2020-07-21 21:21 ` Kees Cook
2020-07-21 10:57 ` [patch V4 02/15] entry: Provide generic syscall entry functionality Thomas Gleixner
2020-07-21 21:38 ` Kees Cook
2020-07-22 7:34 ` Thomas Gleixner
2020-07-22 7:54 ` peterz
2020-07-21 10:57 ` [patch V4 03/15] entry: Provide generic syscall exit function Thomas Gleixner
2020-07-27 22:37 ` Andy Lutomirski
2020-07-21 10:57 ` [patch V4 04/15] entry: Provide generic interrupt entry/exit code Thomas Gleixner
2020-07-27 22:39 ` Andy Lutomirski
2020-07-29 12:18 ` Thomas Gleixner
2020-07-21 10:57 ` [patch V4 05/15] entry: Provide infrastructure for work before exiting to guest mode Thomas Gleixner
2020-07-21 10:57 ` [patch V4 06/15] x86/entry: Consolidate check_user_regs() Thomas Gleixner
2020-07-27 22:39 ` Andy Lutomirski
2020-07-21 10:57 ` [patch V4 07/15] x86/entry: Consolidate 32/64 bit syscall entry Thomas Gleixner
2020-07-21 10:57 ` [patch V4 08/15] x86/entry: Move user return notifier out of loop Thomas Gleixner
2020-07-21 10:57 ` [patch V4 09/15] x86/ptrace: Provide pt_regs helper for entry/exit Thomas Gleixner
2020-07-21 10:57 ` [patch V4 10/15] x86/entry: Use generic syscall entry function Thomas Gleixner
2020-07-21 21:47 ` Kees Cook [this message]
2020-07-22 18:25 ` Thomas Gleixner
2020-07-21 10:57 ` [patch V4 11/15] x86/entry: Use generic syscall exit functionality Thomas Gleixner
2020-07-21 21:47 ` Kees Cook
2020-07-21 10:57 ` [patch V4 12/15] x86/entry: Cleanup idtentry_entry/exit_user Thomas Gleixner
2020-07-21 21:48 ` Kees Cook
2020-07-21 10:57 ` [patch V4 13/15] x86/entry: Use generic interrupt entry/exit code Thomas Gleixner
2020-07-21 10:57 ` [patch V4 14/15] x86/entry: Cleanup idtentry_enter/exit Thomas Gleixner
2020-07-21 21:48 ` Kees Cook
2020-07-21 10:57 ` [patch V4 15/15] x86/kvm: Use generic exit to guest work function Thomas Gleixner
2020-07-21 20:27 ` Sean Christopherson
2020-07-22 7:40 ` Thomas Gleixner
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