From: Peter Zijlstra <peterz@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: Alexander Popov <alex.popov@linux.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Borislav Petkov <bp@alien8.de>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] gcc-plugins/stackleak: Use noinstr in favor of notrace
Date: Sun, 6 Feb 2022 12:58:16 +0100 [thread overview]
Message-ID: <20220206115816.GA23216@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220202001918.4104428-1-keescook@chromium.org>
On Tue, Feb 01, 2022 at 04:19:18PM -0800, Kees Cook wrote:
> While the stackleak plugin was already using notrace, objtool is now a
> bit more picky. Update the notrace uses to noinstr. Silences these
> warnings:
>
> vmlinux.o: warning: objtool: do_syscall_64()+0x9: call to stackleak_track_stack() leaves .noinstr.text section
> vmlinux.o: warning: objtool: do_int80_syscall_32()+0x9: call to stackleak_track_stack() leaves .noinstr.text section
> vmlinux.o: warning: objtool: exc_general_protection()+0x22: call to stackleak_track_stack() leaves .noinstr.text section
> vmlinux.o: warning: objtool: fixup_bad_iret()+0x20: call to stackleak_track_stack() leaves .noinstr.text section
> vmlinux.o: warning: objtool: do_machine_check()+0x27: call to stackleak_track_stack() leaves .noinstr.text section
> vmlinux.o: warning: objtool: .text+0x5346e: call to stackleak_erase() leaves .noinstr.text section
> vmlinux.o: warning: objtool: .entry.text+0x143: call to stackleak_erase() leaves .noinstr.text section
> vmlinux.o: warning: objtool: .entry.text+0x10eb: call to stackleak_erase() leaves .noinstr.text section
> vmlinux.o: warning: objtool: .entry.text+0x17f9: call to stackleak_erase() leaves .noinstr.text section
>
> Cc: Alexander Popov <alex.popov@linux.com>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Link: https://lore.kernel.org/lkml/YYENAKB0igNFnFmK@hirez.programming.kicks-ass.net/
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> Is it correct to exclude .noinstr.text here? That means any functions called in
> there will have their stack utilization untracked. This doesn't seem right to me,
> though. Shouldn't stackleak_track_stack() just be marked noinstr instead?
This patch is right. stackleak_track_stack() cannot be marked noinstr
becaues it accesses things that might not be there.
Consider what happens if we pull the PTI page-table swap into the
noinstr C part.
> @@ -446,6 +447,8 @@ static bool stackleak_gate(void)
> return false;
> if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13))
> return false;
> + if (!strncmp(TREE_STRING_POINTER(section), ".noinstr.text", 13))
> + return false;
For paranoia's sake I'd like .entry.text added there as well.
> }
>
> return track_frame_size >= 0;
next prev parent reply other threads:[~2022-02-06 11:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-02 0:19 [PATCH] gcc-plugins/stackleak: Use noinstr in favor of notrace Kees Cook
2022-02-02 10:45 ` Mark Rutland
2022-02-03 19:33 ` Linus Torvalds
2022-02-06 11:58 ` Peter Zijlstra [this message]
2022-02-06 16:46 ` Kees Cook
2022-02-06 20:40 ` Peter Zijlstra
2022-02-07 2:57 ` Kees Cook
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