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author | Joel Fernandes (Google) <joel@joelfernandes.org> | 2019-04-11 16:24:21 -0400 |
---|---|---|
committer | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-05-28 09:03:35 -0700 |
commit | 056b89e7e699742cc060ce722d3f26effe51b4aa (patch) | |
tree | d2aac68d6dcbca74f3e39a1b246035d775173721 /kernel/rcu/srcutree.c | |
parent | 54e6c11b9e74fd780e52f95c3eed313e0f4e6b7e (diff) | |
download | linux-056b89e7e699742cc060ce722d3f26effe51b4aa.tar.bz2 |
module: Make srcu_struct ptr array as read-only
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>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'kernel/rcu/srcutree.c')
0 files changed, 0 insertions, 0 deletions