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authorKees Cook <keescook@chromium.org>2017-08-16 13:00:58 -0700
committerKees Cook <keescook@chromium.org>2018-01-15 12:08:04 -0800
commit5905429ad85657c28d93ec3d826ddeea1f44c3ce (patch)
tree57fe66f71ea19aa2305ee2085bdd1809e946a136 /arch/Kconfig
parentfork: Define usercopy region in thread_stack slab caches (diff)
downloadlinux-dev-5905429ad85657c28d93ec3d826ddeea1f44c3ce.tar.xz
linux-dev-5905429ad85657c28d93ec3d826ddeea1f44c3ce.zip
fork: Provide usercopy whitelisting for task_struct
While the blocked and saved_sigmask fields of task_struct are copied to userspace (via sigmask_to_save() and setup_rt_frame()), it is always copied with a static length (i.e. sizeof(sigset_t)). The only portion of task_struct that is potentially dynamically sized and may be copied to userspace is in the architecture-specific thread_struct at the end of task_struct. cache object allocation: kernel/fork.c: alloc_task_struct_node(...): return kmem_cache_alloc_node(task_struct_cachep, ...); dup_task_struct(...): ... tsk = alloc_task_struct_node(node); copy_process(...): ... dup_task_struct(...) _do_fork(...): ... copy_process(...) example usage trace: arch/x86/kernel/fpu/signal.c: __fpu__restore_sig(...): ... struct task_struct *tsk = current; struct fpu *fpu = &tsk->thread.fpu; ... __copy_from_user(&fpu->state.xsave, ..., state_size); fpu__restore_sig(...): ... return __fpu__restore_sig(...); arch/x86/kernel/signal.c: restore_sigcontext(...): ... fpu__restore_sig(...) This introduces arch_thread_struct_whitelist() to let an architecture declare specifically where the whitelist should be within thread_struct. If undefined, the entire thread_struct field is left whitelisted. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Laura Abbott <labbott@redhat.com> Cc: "Mickaël Salaün" <mic@digikod.net> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Rik van Riel <riel@redhat.com>
Diffstat (limited to '')
-rw-r--r--arch/Kconfig11
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 400b9e1b2f27..8911ff37335a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -242,6 +242,17 @@ config ARCH_INIT_TASK
config ARCH_TASK_STRUCT_ALLOCATOR
bool
+config HAVE_ARCH_THREAD_STRUCT_WHITELIST
+ bool
+ depends on !ARCH_TASK_STRUCT_ALLOCATOR
+ help
+ An architecture should select this to provide hardened usercopy
+ knowledge about what region of the thread_struct should be
+ whitelisted for copying to userspace. Normally this is only the
+ FPU registers. Specifically, arch_thread_struct_whitelist()
+ should be implemented. Without this, the entire thread_struct
+ field in task_struct will be left whitelisted.
+
# Select if arch has its private alloc_thread_stack() function
config ARCH_THREAD_STACK_ALLOCATOR
bool