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From: Petr Mladek <pmladek@suse.com>
To: Jessica Yu <jeyu@kernel.org>
Cc: Torsten Duwe <duwe@lst.de>, Will Deacon <will.deacon@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Julien Thierry <julien.thierry@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Ingo Molnar <mingo@redhat.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH] arm64/module: use mod->klp_info section header information
Date: Thu, 25 Oct 2018 10:08:16 +0200	[thread overview]
Message-ID: <20181025080816.525dppcfrrevf6jc@pathway.suse.cz> (raw)
In-Reply-To: <20181023175553.gaobskk26koft6s2@linux-8ccs>

On Tue 2018-10-23 19:55:54, Jessica Yu wrote:
> The arm64 module loader keeps a pointer into info->sechdrs to keep track
> of section header information for .plt section(s). A pointer to the
> relevent section header (struct elf64_shdr) in info->sechdrs is stored
> in mod->arch.{init,core}.plt. This pointer may be accessed while
> applying relocations in apply_relocate_add() for example. And unlike
> normal modules, livepatch modules can call apply_relocate_add() after
> module load. But the info struct (and therefore info->sechdrs) gets
> freed at the end of load_module() and so mod->arch.{init,core}.plt
> becomes an invalid pointer after the module is done loading.
> 
> Luckily, livepatch modules already keep a copy of Elf section header
> information in mod->klp_info. So make sure livepatch modules on arm64
> have access to the section headers in klp_info and set
> mod->arch.{init,core}.plt to the appropriate section header in
> mod->klp_info so that they can call apply_relocate_add() even after
> module load.
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index f475f30eed8c..f3ac04cc9fc3 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3367,6 +3367,8 @@ int __weak module_finalize(const Elf_Ehdr *hdr,
> 
> static int post_relocation(struct module *mod, const struct load_info *info)
> {
> +	int err;
> +
> 	/* Sort exception table now relocations are done. */
> 	sort_extable(mod->extable, mod->extable + mod->num_exentries);
> 
> @@ -3377,8 +3379,18 @@ static int post_relocation(struct module *mod, const struct load_info *info)
> 	/* Setup kallsyms-specific fields. */
> 	add_kallsyms(mod, info);
> 
> +	if (is_livepatch_module(mod)) {
> +		err = copy_module_elf(mod, info);
> +		if (err < 0)
> +			return err;
> +	}
> +
> 	/* Arch-specific module finalizing. */
> -	return module_finalize(info->hdr, info->sechdrs, mod);
> +	err = module_finalize(info->hdr, info->sechdrs, mod);
> +	if (err < 0)

	if (err < 0 && is_livepatch_module(mod))

> +		free_module_elf(mod);
> +
> +	return err;
> }

Also we need to free the copied stuff in load_module() when
anything called after post_relocation() fails. I think
that the following would work:

--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3823,6 +3823,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	kfree(mod->args);
  free_arch_cleanup:
 	module_arch_cleanup(mod);
+	if (is_livepatch_module(mod))
+		free_module_elf(mod);
  free_modinfo:
 	free_modinfo(mod);
  free_unload:


But I suggest to just move copy_module_elf() up and keep
calling it from load_module() directly. It would make
the error handling more clear.

Best Regards,
Petr

  parent reply	other threads:[~2018-10-25  8:08 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-01 14:09 [PATCH v3 0/4] arm64 live patching Torsten Duwe
2018-10-01 14:16 ` [PATCH v3 1/4] DYNAMIC_FTRACE configurable with and without REGS Torsten Duwe
2018-10-01 14:52   ` Ard Biesheuvel
2018-10-01 15:03     ` Torsten Duwe
2018-10-01 15:06       ` Ard Biesheuvel
2018-10-01 15:10         ` Torsten Duwe
2018-10-01 15:14           ` Steven Rostedt
2018-10-01 14:16 ` [PATCH v3 2/4] arm64: implement ftrace with regs Torsten Duwe
2018-10-01 15:57   ` Ard Biesheuvel
2018-10-02 10:02     ` Torsten Duwe
2018-10-02 10:39       ` Ard Biesheuvel
2018-10-02 11:27   ` Mark Rutland
2018-10-02 12:18     ` Torsten Duwe
2018-10-02 12:57       ` Mark Rutland
2018-10-01 14:16 ` [PATCH v3 3/4] arm64: implement live patching Torsten Duwe
2018-10-17 13:39   ` Miroslav Benes
2018-10-18 12:58     ` Jessica Yu
2018-10-19 11:59       ` Miroslav Benes
2018-10-19 12:18         ` Jessica Yu
2018-10-19 15:14           ` Miroslav Benes
2018-10-19 13:46         ` Torsten Duwe
2018-10-19 13:52       ` Ard Biesheuvel
2018-10-19 15:21         ` Miroslav Benes
2018-10-20 14:10           ` Ard Biesheuvel
2018-10-22 12:53             ` Miroslav Benes
2018-10-22 14:54               ` Torsten Duwe
2018-10-23 17:55   ` [PATCH] arm64/module: use mod->klp_info section header information Jessica Yu
2018-10-23 19:32     ` kbuild test robot
2018-10-24 11:57     ` Miroslav Benes
2018-10-25  8:08     ` Petr Mladek [this message]
2018-10-25  9:00       ` Miroslav Benes
2018-10-25 11:42         ` Jessica Yu
2018-10-26 17:25     ` [PATCH v2] arm64/module: use mod->klp_info section header information for livepatch modules Jessica Yu
2018-10-29 13:24       ` Miroslav Benes
2018-10-29 13:32         ` Jessica Yu
2018-10-29 15:28       ` Will Deacon
2018-10-30 13:19         ` Jessica Yu
2018-11-01 15:18           ` Miroslav Benes
2018-11-01 16:07           ` Will Deacon
2018-11-05 12:30             ` Ard Biesheuvel
2018-11-05 17:57   ` [PATCH] arm64/module: use plt section indices for relocations Jessica Yu
2018-11-05 18:04     ` Ard Biesheuvel
2018-11-05 18:53     ` [PATCH v2] " Jessica Yu
2018-11-05 18:56       ` Ard Biesheuvel
2018-11-05 19:26       ` Will Deacon
2018-11-05 19:49         ` Jessica Yu
2018-11-06  9:44         ` Miroslav Benes
2018-10-01 14:16 ` [PATCH v3 4/4] arm64: reliable stacktraces Torsten Duwe

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