From: Jessica Yu <jeyu@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Kees Cook <keescook@chromium.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Miroslav Benes <mbenes@suse.cz>,
Mark Rutland <mark.rutland@arm.com>, nd <nd@arm.com>
Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX
Date: Mon, 31 Aug 2020 11:46:51 +0200 [thread overview]
Message-ID: <20200831094651.GA16385@linux-8ccs> (raw)
In-Reply-To: <20200821123036.GA21158@willie-the-truck>
+++ Will Deacon [21/08/20 13:30 +0100]:
[snipped]
>> > > > So module_enforce_rwx_sections() is already called after
>> > > > module_frob_arch_sections() - which really baffled me at first, since
>> > > > sh_type and sh_flags should have been set already in
>> > > > module_frob_arch_sections().
>> > > >
>> > > > I added some debug prints to see which section the module code was
>> > > > tripping on, and it was .text.ftrace_trampoline. See this snippet from
>> > > > arm64's module_frob_arch_sections():
>> > > >
>> > > > else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) &&
>> > > > !strcmp(secstrings + sechdrs[i].sh_name,
>> > > > ".text.ftrace_trampoline"))
>> > > > tramp = sechdrs + i;
>> > > >
>> > > > Since Mauro's config doesn't have CONFIG_DYNAMIC_FTRACE enabled, tramp
>> > > > is never set here and the if (tramp) check at the end of the function
>> > > > fails, so its section flags are never set, so they remain WAX and fail
>> > > > the rwx check.
>> > >
>> > > Right. Our module.lds does not go through the preprocessor, so we
>> > > cannot add the #ifdef check there currently. So we should either drop
>> > > the IS_ENABLED() check here, or simply rename the section, dropping
>> > > the .text prefix (which doesn't seem to have any significance outside
>> > > this context)
>> > >
>> > > I'll leave it to Will to make the final call here.
>> >
>> > Why don't we just preprocess the linker script, like we do for the main
>> > kernel?
>> >
>>
>> That should work as well, I just haven't checked how straight-forward
>> it is to change that.
>
>Ok, if it's _not_ straightforward, then let's just drop the IS_ENABLED()
>altogether.
Unfortunately I've been getting more reports about this issue, so let's just
get the aforementioned workaround merged first. Does the following look OK?
diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c
index 0ce3a28e3347..2e224435c024 100644
--- a/arch/arm64/kernel/module-plts.c
+++ b/arch/arm64/kernel/module-plts.c
@@ -305,8 +305,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
mod->arch.core.plt_shndx = i;
else if (!strcmp(secstrings + sechdrs[i].sh_name, ".init.plt"))
mod->arch.init.plt_shndx = i;
- else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) &&
- !strcmp(secstrings + sechdrs[i].sh_name,
+ else if (!strcmp(secstrings + sechdrs[i].sh_name,
".text.ftrace_trampoline"))
tramp = sechdrs + i;
else if (sechdrs[i].sh_type == SHT_SYMTAB)
If so I'll turn it into a formal patch and we can get that merged in the next -rc.
Thanks,
Jessica
next prev parent reply other threads:[~2020-08-31 9:46 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-03 17:13 [PATCH v2] module: Harden STRICT_MODULE_RWX Peter Zijlstra
2020-04-03 20:31 ` Kees Cook
2020-04-08 15:32 ` Jessica Yu
2020-04-08 15:43 ` [PATCH] module: break nested ARCH_HAS_STRICT_MODULE_RWX and STRICT_MODULE_RWX #ifdefs Jessica Yu
2020-04-08 15:57 ` [PATCH v2] module: Harden STRICT_MODULE_RWX Peter Zijlstra
2020-04-08 16:20 ` Jessica Yu
2020-08-08 8:12 ` Mauro Carvalho Chehab
2020-08-10 9:25 ` Jessica Yu
2020-08-10 15:06 ` Jessica Yu
2020-08-11 14:34 ` Mauro Carvalho Chehab
2020-08-11 14:55 ` peterz
2020-08-11 15:27 ` Mauro Carvalho Chehab
2020-08-11 16:01 ` Jessica Yu
2020-08-11 16:57 ` Will Deacon
2020-08-11 17:59 ` peterz
2020-08-11 21:29 ` Peter Zijlstra
2020-08-12 8:56 ` Ard Biesheuvel
2020-08-12 10:40 ` peterz
2020-08-12 11:41 ` Jessica Yu
2020-08-12 13:14 ` H.J. Lu
2020-08-12 12:56 ` Will Deacon
2020-08-12 14:15 ` Szabolcs Nagy
2020-08-12 16:00 ` Jessica Yu
2020-08-12 16:37 ` Ard Biesheuvel
2020-08-12 16:42 ` Szabolcs Nagy
2020-08-13 9:00 ` Will Deacon
2020-08-12 20:00 ` Peter Zijlstra
2020-08-13 8:36 ` Ard Biesheuvel
2020-08-13 13:04 ` Jessica Yu
2020-08-13 13:07 ` Ard Biesheuvel
2020-08-21 12:20 ` Will Deacon
2020-08-21 12:27 ` Ard Biesheuvel
2020-08-21 12:30 ` Will Deacon
2020-08-22 13:47 ` Ard Biesheuvel
2020-08-24 15:24 ` Jessica Yu
2020-08-25 1:54 ` Masahiro Yamada
2020-08-31 9:46 ` Jessica Yu [this message]
2020-08-31 10:42 ` Masahiro Yamada
2020-08-31 13:25 ` Ard Biesheuvel
2020-08-31 15:31 ` Jessica Yu
2020-08-31 15:46 ` Masahiro Yamada
2020-09-03 12:37 ` Jessica Yu
2020-09-01 12:51 ` Will Deacon
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