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kernel: wipe TLS when dropping to user mode

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For threads that run in supervisor mode for some time before
synchronously dropping to user mode, re-initialize the TLS
area to prevent leakage of potentially sensitive information.

We did this already for CONFIG_THREAD_USERSPACE_LOCAL_DATA
but not the new CONFIG_THREAD_LOCAL_STORAGE.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2020-10-24 13:04:04 -07:00 • committed by Ioannis Glaropoulos
commit 0e30c6a0fa
1 changed files with 7 additions and 1 deletions
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8
kernel/thread.c
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@ -493,7 +493,8 @@ static char *setup_thread_stack(struct k_thread *new_thread,
*((uint32_t *)stack_buf_start) = STACK_SENTINEL;
#endif /* CONFIG_STACK_SENTINEL */
#ifdef CONFIG_THREAD_LOCAL_STORAGE
delta += arch_tls_stack_setup(new_thread, (stack_ptr - delta));
/* TLS is always last within the stack buffer */
delta += arch_tls_stack_setup(new_thread, stack_ptr);
#endif /* CONFIG_THREAD_LOCAL_STORAGE */
#ifdef CONFIG_THREAD_USERSPACE_LOCAL_DATA
size_t tls_size = sizeof(struct _thread_userspace_local_data);
@ -838,6 +839,11 @@ FUNC_NORETURN void k_thread_user_mode_enter(k_thread_entry_t entry,
#ifdef CONFIG_THREAD_USERSPACE_LOCAL_DATA
memset(_current->userspace_local_data, 0,
sizeof(struct _thread_userspace_local_data));
#endif
#ifdef CONFIG_THREAD_LOCAL_STORAGE
arch_tls_stack_setup(_current,
(char *)(_current->stack_info.start +
_current->stack_info.size));
#endif
arch_user_mode_enter(entry, p1, p2, p3);
#else