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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com,
	jbaron@akamai.com, torvalds@linux-foundation.org,
	tglx@linutronix.de, mingo@kernel.org, namit@vmware.com,
	hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org,
	jeyu@kernel.org
Subject: Re: [PATCH v4 15/16] module: Move where we mark modules RO,X
Date: Thu, 24 Oct 2019 13:31:15 -0500	[thread overview]
Message-ID: <20191024183115.jomddpijq5u453qc@treble> (raw)
In-Reply-To: <20191024105904.GB4131@hirez.programming.kicks-ass.net>

On Thu, Oct 24, 2019 at 12:59:04PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 23, 2019 at 12:15:14PM -0500, Josh Poimboeuf wrote:
> > On Wed, Oct 23, 2019 at 05:16:54PM +0200, Peter Zijlstra wrote:
> > > @@ -157,6 +158,14 @@ static int __apply_relocate_add(Elf64_Sh
> > >  
> > >  		val = sym->st_value + rel[i].r_addend;
> > >  
> > > +		/*
> > > +		 * .klp.rela.* sections should only contain module
> > > +		 * related RELAs. All core-kernel RELAs should be in
> > > +		 * normal .rela.* sections and be applied when loading
> > > +		 * the patch module itself.
> > > +		 */
> > > +		WARN_ON_ONCE(klp && core_kernel_text(val));
> > > +
> > 
> > This isn't quite true, we also use .klp.rela sections to access
> > unexported vmlinux symbols.
> 
> Yes, you said in that earlier email. That all makes it really hard to
> validate this. But unless we validate it, it will stay buggy :/
> 
> Hmmm.... /me ponders
> 
> The alternative would be to apply the .klp.rela.* sections twice, once
> at patch-module load time and then apply those core_kernel_text()
> entries, and then once later and skip over them.
> 
> How's this?

How about something like this?  Completely untested, but if you agree
with this approach I could hack up kpatch-build to test it properly.

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index ab4a4606d19b..597bf32bc591 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -239,6 +239,17 @@ static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 		if (ret)
 			return ret;
 
+		/*
+		 * Prevent module patches from using livepatch relas for
+		 * vmlinux symbols.  Presumably such symbols are exported and
+		 * normal relas can instead be used at patch module loading
+		 * time.
+		 */
+		if (!vmlinux && core_kernel_text(addr)) {
+			pr_err("unsupported livepatch symbol\n");
+			return -EINVAL;
+		}
+
 		sym->st_value = addr;
 	}
 


  reply	other threads:[~2019-10-24 18:31 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  7:35 [PATCH v4 00/16] Rewrite x86/ftrace to use text_poke (and more) Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 01/16] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 02/16] x86/alternatives: Update int3_emulate_push() comment Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 03/16] x86/alternatives,jump_label: Provide better text_poke() batching interface Peter Zijlstra
2019-10-21  8:48   ` Ingo Molnar
2019-10-21  9:21     ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 04/16] x86/alternatives: Add and use text_gen_insn() helper Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 05/16] x86/ftrace: Use text_poke() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 06/16] x86/mm: Remove set_kernel_text_r[ow]() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 07/16] x86/alternative: Add text_opcode_size() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 08/16] x86/ftrace: Use text_gen_insn() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 09/16] x86/alternative: Remove text_poke_loc::len Peter Zijlstra
2019-10-21  8:58   ` Ingo Molnar
2019-10-21  9:02     ` Ingo Molnar
2019-10-18  7:35 ` [PATCH v4 10/16] x86/alternative: Shrink text_poke_loc Peter Zijlstra
2019-10-21  9:01   ` Ingo Molnar
2019-10-21  9:25     ` Peter Zijlstra
2019-10-21  9:33       ` Ingo Molnar
2019-10-18  7:35 ` [PATCH v4 11/16] x86/kprobes: Convert to text-patching.h Peter Zijlstra
2019-10-21 14:57   ` Masami Hiramatsu
2019-10-18  7:35 ` [PATCH v4 12/16] x86/kprobes: Fix ordering Peter Zijlstra
2019-10-22  1:35   ` Masami Hiramatsu
2019-10-22 10:31     ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 13/16] arm/ftrace: Use __patch_text_real() Peter Zijlstra
2019-10-28 16:25   ` Will Deacon
2019-10-28 16:34     ` Peter Zijlstra
2019-10-28 16:35       ` Peter Zijlstra
2019-10-28 16:47       ` Will Deacon
2019-10-28 16:55         ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 14/16] module: Remove set_all_modules_text_*() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 15/16] module: Move where we mark modules RO,X Peter Zijlstra
2019-10-21 13:53   ` Josh Poimboeuf
2019-10-21 14:14     ` Peter Zijlstra
2019-10-21 15:34       ` Peter Zijlstra
2019-10-21 15:44         ` Peter Zijlstra
2019-10-21 16:11         ` Peter Zijlstra
2019-10-22 11:31           ` Heiko Carstens
2019-10-22 12:31             ` Peter Zijlstra
2019-10-23 11:48       ` Peter Zijlstra
2019-10-23 15:16         ` Peter Zijlstra
2019-10-23 17:15           ` Josh Poimboeuf
2019-10-24 10:59             ` Peter Zijlstra
2019-10-24 18:31               ` Josh Poimboeuf [this message]
2019-10-24 20:33                 ` Peter Zijlstra
2019-10-23 17:00         ` Josh Poimboeuf
2019-10-24 13:16           ` Peter Zijlstra
2019-10-25  6:44             ` Petr Mladek
2019-10-25  8:43               ` Peter Zijlstra
2019-10-25 10:06                 ` Peter Zijlstra
2019-10-25 13:50                   ` Josh Poimboeuf
2019-10-26  1:17                   ` Josh Poimboeuf
2019-10-28 10:07                     ` Peter Zijlstra
2019-10-28 10:43                     ` Peter Zijlstra
2019-10-25  9:16               ` Peter Zijlstra
2019-10-22  2:21   ` Steven Rostedt
2019-10-22 20:24     ` Peter Zijlstra
2019-10-22 20:40       ` Steven Rostedt
2019-10-23  9:07         ` Peter Zijlstra
2019-10-23 18:52       ` Steven Rostedt
2019-10-24 10:16         ` Peter Zijlstra
2019-10-24 10:18           ` Peter Zijlstra
2019-10-24 15:00           ` Steven Rostedt
2019-10-24 16:43             ` Peter Zijlstra
2019-10-24 18:17               ` Steven Rostedt
2019-10-24 20:24                 ` Peter Zijlstra
2019-10-24 20:28                   ` Steven Rostedt
2019-10-18  7:35 ` [PATCH v4 16/16] ftrace: Merge ftrace_module_{init,enable}() Peter Zijlstra
2019-10-18  8:20   ` Peter Zijlstra
2019-10-21  9:09 ` [PATCH v4 00/16] Rewrite x86/ftrace to use text_poke (and more) Ingo Molnar
2019-10-21 13:38   ` Steven Rostedt

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