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authorJoel Fernandes (Google) <joel@joelfernandes.org>2019-04-11 16:24:21 -0400
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-05-28 09:03:35 -0700
commit056b89e7e699742cc060ce722d3f26effe51b4aa (patch)
treed2aac68d6dcbca74f3e39a1b246035d775173721 /kernel
parent54e6c11b9e74fd780e52f95c3eed313e0f4e6b7e (diff)
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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')
0 files changed, 0 insertions, 0 deletions