diff options
Diffstat (limited to 'arch/x86/kernel/shstk.c')
| -rw-r--r-- | arch/x86/kernel/shstk.c | 41 |
1 files changed, 39 insertions, 2 deletions
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 3cb85224d856..bd9cdc3a7338 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -47,7 +47,7 @@ static unsigned long alloc_shstk(unsigned long size) unsigned long addr, unused; mmap_write_lock(mm); - addr = do_mmap(NULL, addr, size, PROT_READ, flags, + addr = do_mmap(NULL, 0, size, PROT_READ, flags, VM_SHADOW_STACK | VM_WRITE, 0, &unused, NULL); mmap_write_unlock(mm); @@ -126,6 +126,37 @@ void reset_thread_features(void) current->thread.features_locked = 0; } +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags, + unsigned long stack_size) +{ + struct thread_shstk *shstk = &tsk->thread.shstk; + unsigned long addr, size; + + /* + * If shadow stack is not enabled on the new thread, skip any + * switch to a new shadow stack. + */ + if (!features_enabled(ARCH_SHSTK_SHSTK)) + return 0; + + /* + * For CLONE_VM, except vfork, the child needs a separate shadow + * stack. + */ + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM) + return 0; + + size = adjust_shstk_size(stack_size); + addr = alloc_shstk(size); + if (IS_ERR_VALUE(addr)) + return addr; + + shstk->base = addr; + shstk->size = size; + + return addr + size; +} + void shstk_free(struct task_struct *tsk) { struct thread_shstk *shstk = &tsk->thread.shstk; @@ -134,7 +165,13 @@ void shstk_free(struct task_struct *tsk) !features_enabled(ARCH_SHSTK_SHSTK)) return; - if (!tsk->mm) + /* + * When fork() with CLONE_VM fails, the child (tsk) already has a + * shadow stack allocated, and exit_thread() calls this function to + * free it. In this case the parent (current) and the child share + * the same mm struct. + */ + if (!tsk->mm || tsk->mm != current->mm) return; unmap_shadow_stack(shstk->base, shstk->size); |