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
next prev 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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