From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
paulmck@linux.vnet.ibm.com, rostedt@goodmis.org,
mathieu.desnoyers@efficios.com, rcu@vger.kernel.org,
kernel-hardening@lists.openwall.com, kernel-team@android.com,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
"Paul E. McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH] module: Make srcu_struct ptr array as read-only
Date: Thu, 11 Apr 2019 16:24:21 -0400 [thread overview]
Message-ID: <20190411202421.131779-1-joel@joelfernandes.org> (raw)
Since commit title ("srcu: Allocate per-CPU data for DEFINE_SRCU() in
modules"), modules that call DEFINE_{STATIC,}SRCU will have a new array
of srcu_struct pointers, which is used by srcu code to initialize and
clean up these structures and save valuable per-cpu reserved space.
There is no reason for this array of pointers to be writable, and can
cause security or other hidden bugs. Mark these are read-only after the
module init has completed.
Tested with the following diff to ensure array not writable:
(diff is a bit reduced to avoid patch command getting confused)
a/kernel/module.c
b/kernel/module.c
-3506,6 +3506,14 static noinline int do_init_module [snip]
rcu_assign_pointer(mod->kallsyms, &mod->core_kallsyms);
#endif
module_enable_ro(mod, true);
+
+ if (mod->srcu_struct_ptrs) {
+ // Check if srcu_struct_ptrs access is possible
+ char x = *(char *)mod->srcu_struct_ptrs;
+ *(char *)mod->srcu_struct_ptrs = 0;
+ *(char *)mod->srcu_struct_ptrs = x;
+ }
+
mod_tree_remove_init(mod);
disable_ro_nx(&mod->init_layout);
module_arch_freeing_init(mod);
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: paulmck@linux.vnet.ibm.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: rcu@vger.kernel.org
Cc: kernel-hardening@lists.openwall.com
Cc: kernel-team@android.com
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
This single patch superceded the patches at:
https://lore.kernel.org/patchwork/patch/1060298/
https://lore.kernel.org/patchwork/patch/1060298/
include/linux/srcutree.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 8af1824c46a8..9cfcc8a756ae 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -123,7 +123,7 @@ struct srcu_struct {
#ifdef MODULE
# define __DEFINE_SRCU(name, is_static) \
is_static struct srcu_struct name; \
- struct srcu_struct *__srcu_struct_##name \
+ struct srcu_struct * const __srcu_struct_##name \
__section("___srcu_struct_ptrs") = &name
#else
# define __DEFINE_SRCU(name, is_static) \
--
2.21.0.392.gf8f6787159e-goog
next reply other threads:[~2019-04-11 20:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-11 20:24 Joel Fernandes (Google) [this message]
2019-04-11 21:31 ` [PATCH] module: Make srcu_struct ptr array as read-only Paul E. McKenney
2019-04-12 2:14 ` Joel Fernandes
2019-04-12 2:35 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190411202421.131779-1-joel@joelfernandes.org \
--to=joel@joelfernandes.org \
--cc=jiangshanlai@gmail.com \
--cc=josh@joshtriplett.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=kernel-team@android.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=mathieu.desnoyers@efficios.com \
--cc=paulmck@linux.ibm.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).