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kernel: fix TOCTTOU issue in k_thread_name_set

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Previously, a racing write to the provided string could result
in up to CONFIG_THREAD_MAX_NAME_LEN-2 bytes after the end
of user-accessible memory being leaked into the thread name.

For now, make a temporary copy. In an ideal world this could
copy directly from userspace into the thread name, but that
violates the current vrfy / impl split.

Signed-off-by: James Harris <james.harris@intel.com>
This commit is contained in:
James Harris 2021-03-08 09:23:49 -08:00 committed by Anas Nashif
parent 6f82ebe2e8
commit 33c9be90cc
1 changed files with 7 additions and 8 deletions
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15
kernel/thread.c
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@ -237,8 +237,7 @@ int z_impl_k_thread_name_set(struct k_thread *thread, const char *value)
static inline int z_vrfy_k_thread_name_set(struct k_thread *t, const char *str)
{
#ifdef CONFIG_THREAD_NAME
size_t len;
int err;
char name[CONFIG_THREAD_MAX_NAME_LEN];
if (t != NULL) {
if (Z_SYSCALL_OBJ(t, K_OBJ_THREAD) != 0) {
@ -246,15 +245,15 @@ static inline int z_vrfy_k_thread_name_set(struct k_thread *t, const char *str)
}
}
len = z_user_string_nlen(str, CONFIG_THREAD_MAX_NAME_LEN, &err);
if (err != 0) {
return -EFAULT;
}
if (Z_SYSCALL_MEMORY_READ(str, len) != 0) {
/* In theory we could copy directly into thread->name, but
* the current z_vrfy / z_impl split does not provide a
* means of doing so.
*/
if (z_user_string_copy(name, (char *)str, sizeof(name)) != 0) {
return -EFAULT;
}
return z_impl_k_thread_name_set(t, str);
return z_impl_k_thread_name_set(t, name);
#else
return -ENOSYS;
#endif /* CONFIG_THREAD_NAME */