From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Brian Gerst <brgerst@gmail.com>
Subject: Re: [PATCH v4 2/9] x86/kthread,dumpstack: Set task_pt_regs->cs.RPL=3 for kernel threads
Date: Wed, 17 Mar 2021 19:36:25 -0500 [thread overview]
Message-ID: <20210318003625.necz6ygibfqocicz@treble> (raw)
In-Reply-To: <cbe4b7d77b62419749c5ab242ab0270026dc5062.1616004689.git.luto@kernel.org>
On Wed, Mar 17, 2021 at 11:12:41AM -0700, Andy Lutomirski wrote:
> @@ -163,6 +163,19 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
> /* Kernel thread ? */
> if (unlikely(p->flags & PF_KTHREAD)) {
> memset(childregs, 0, sizeof(struct pt_regs));
> +
> + /*
> + * Even though there is no real user state here, these
> + * are were user regs belong, and kernel_execve() will
s/were/where/
> + * overwrite them with user regs. Put an obviously
> + * invalid value that nonetheless causes user_mode(regs)
> + * to return true in CS.
> + *
> + * This also prevents the unwinder from thinking that there
> + * is invalid kernel state at the top of the stack.
> + */
> + childregs->cs = 3;
> +
> kthread_frame_init(frame, sp, arg);
> return 0;
> }
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
--
Josh
next prev parent reply other threads:[~2021-03-18 0:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 18:12 [PATCH v4 0/9] kentry: A stable bugfix and a bunch of improvements Andy Lutomirski
2021-03-17 18:12 ` [PATCH v4 1/9] x86/dumpstack: Remove unnecessary range check fetching opcode bytes Andy Lutomirski
2021-03-17 18:12 ` [PATCH v4 2/9] x86/kthread,dumpstack: Set task_pt_regs->cs.RPL=3 for kernel threads Andy Lutomirski
2021-03-18 0:36 ` Josh Poimboeuf [this message]
2021-03-17 18:12 ` [PATCH v4 3/9] x86/entry: Convert ret_from_fork to C Andy Lutomirski
2021-03-18 0:38 ` Josh Poimboeuf
2021-03-19 16:05 ` Thomas Gleixner
2021-03-17 18:12 ` [PATCH v4 4/9] kentry: Simplify the common syscall API Andy Lutomirski
2021-03-19 16:09 ` Thomas Gleixner
2021-03-19 18:07 ` Thomas Gleixner
2021-03-17 18:12 ` [PATCH v4 5/9] kentry: Remove enter_from/exit_to_user_mode() Andy Lutomirski
2021-03-19 18:08 ` Thomas Gleixner
2021-03-17 18:12 ` [PATCH v4 6/9] entry: Make CONFIG_DEBUG_ENTRY available outside x86 Andy Lutomirski
2021-03-17 18:12 ` [PATCH v4 7/9] kentry: Add debugging checks for proper kentry API usage Andy Lutomirski
2021-03-19 16:17 ` Thomas Gleixner
2021-03-19 18:16 ` Thomas Gleixner
2021-03-17 18:12 ` [PATCH v4 8/9] kentry: Check that syscall entries and syscall exits match Andy Lutomirski
2021-03-17 18:12 ` [PATCH v4 9/9] kentry: Verify kentry state in instrumentation_begin/end() Andy Lutomirski
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