Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok

Oleg Nesterov
2023-03-29T17:14:26Z

On 03/28, Gregory Price wrote:
>
> Not sure how I should proceed here,

Can't we just kill this access_ok() in set_syscall_user_dispatch() ?
I don't think it buys too much.

Oleg.

diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 0b6379adff6b..d2e516ece52b 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -43,11 +43,7 @@ bool syscall_user_dispatch(struct pt_regs *regs)
return false;

if (likely(sd->selector)) {
- /*
- * access_ok() is performed once, at prctl time, when
- * the selector is loaded by userspace.
- */
- if (unlikely(__get_user(state, sd->selector))) {
+ if (unlikely(get_user(state, sd->selector))) {
force_exit_sig(SIGSEGV);
return true;
}
@@ -86,9 +82,6 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
if (offset && offset + len <= offset)
return -EINVAL;

- if (selector && !access_ok(selector, sizeof(*selector)))
- return -EFAULT;
-
break;
default:
return -EINVAL;