From: Jessica Yu <jeyu@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Joel Fernandes <joel@joelfernandes.org>,
linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com,
keescook@chromium.org, mathieu.desnoyers@efficios.com,
kernel-hardening@lists.openwall.com, kernel-team@android.com,
rcu@vger.kernel.org
Subject: Re: [PATCH v3 3/3] module: Make __tracepoints_ptrs as read-only
Date: Wed, 17 Apr 2019 17:16:18 +0200 [thread overview]
Message-ID: <20190417151618.GD17099@linux-8ccs> (raw)
In-Reply-To: <20190410204401.62f928ca@gandalf.local.home>
+++ Steven Rostedt [10/04/19 20:44 -0400]:
>On Wed, 10 Apr 2019 16:29:02 -0400
>Joel Fernandes <joel@joelfernandes.org> wrote:
>
>> The srcu structure pointer array is modified at module load time because the
>> array is fixed up by the module loader at load-time with the final locations
>> of the tracepoints right? Basically relocation fixups. At compile time, I
>> believe it is not know what the values in the ptr array are. I believe same
>> is true for the tracepoint ptrs array.
>>
>> Also it needs to be in a separate __tracepoint_ptrs so that this code works:
>>
>>
>> #ifdef CONFIG_TRACEPOINTS
>> mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
>> sizeof(*mod->tracepoints_ptrs),
>> &mod->num_tracepoints);
>> #endif
>>
>> Did I miss some point? Thanks,
>
>But there's a lot of others too. Hmm, does this mean that the RO data
>sections that are in modules are not set to RO?
>
>There's a bunch of separate sections that are RO. Just look in
>include/asm-generic/vmlinux.lds.h under the RO_DATA_SECTION() macro.
>
>A lot of the sections saved in module.c:find_module_sections() are in
>that RO_DATA when compiled as a builtin. Are they not RO when loaded via
>a module?
Unlike the kernel, the module loader does not rely on a linker script
to determine which sections get what protections. On module load, all
sections in a module are looped through and those sections without the
SHF_WRITE flag will be set to RO. For example, when there is a section
filled with structs declared as const or if the section was explicitly
given only the SHF_ALLOC attribute, those will be read-only. As long
as the sections were given the correct section attributes for
read-only, it'll have read-only protection. I see this is already the
case for __param and __ksymtab*/__kcrctab* sections, but I agree that
a full audit would be useful to be consistent with builtin RO
protections.
Hope that helps,
Jessica
next prev parent reply other threads:[~2019-04-17 15:16 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 19:57 [PATCH v3 1/3] module: Prepare for addition of new ro_after_init sections Joel Fernandes (Google)
2019-04-10 19:57 ` [PATCH v3 2/3] module: Make srcu_struct ptr array as read-only post init Joel Fernandes (Google)
2019-04-10 19:57 ` [PATCH v3 3/3] module: Make __tracepoints_ptrs as read-only Joel Fernandes (Google)
2019-04-10 20:11 ` Steven Rostedt
2019-04-10 20:29 ` Joel Fernandes
2019-04-11 0:44 ` Steven Rostedt
2019-04-11 8:21 ` Joel Fernandes
2019-04-11 13:19 ` Steven Rostedt
2019-04-11 20:06 ` Joel Fernandes
2019-04-11 13:44 ` Paul E. McKenney
2019-04-17 15:16 ` Jessica Yu [this message]
2019-04-17 15:36 ` Paul E. McKenney
2019-04-20 11:38 ` Joel Fernandes
2019-04-11 8:32 ` [PATCH v3 1/3] module: Prepare for addition of new ro_after_init sections Miroslav Benes
2019-04-17 13:29 ` Jessica Yu
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