On Mon, Jan 23, 2023 at 04:41:02PM +0100, Oleg Nesterov wrote:
On 01/22, Gregory Price wrote:
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
void __user *data)+{
- struct syscall_user_dispatch *sd = &task->syscall_dispatch;
- struct syscall_user_dispatch_config config;
- if (size != sizeof(struct syscall_user_dispatch_config))
return -EINVAL;- if (test_syscall_work(SYSCALL_USER_DISPATCH))
config.mode = PR_SYS_DISPATCH_ON;- else
config.mode = PR_SYS_DISPATCH_OFF;Stupid question...
Why do we need 2/3 (which reports SYSCALL_USER_DISPATCH in proc/pid/status) then?
Oleg.
Actually a good question.
My original though was: CRIU uses proc/status to determine whether to use seccomp dumping, so i may as well implement the same thing.
On further thought, I think you're right. We can just always read and set these settings regardless of the original state because SUD is not seccomp.
1. if GENERIC_ENTRY is not compiled, and TIF_SYSCALL_USER_DISPATCH is not available, these settings get ignored anyway. 2. if disabled, offset/len/selector is guaranteed to be off 3. if you try to set something other than the above then this will fail anyway (see: set_syscall_user_dispatch)
ergo 4. It's always say to read/write these settings. As with anything else you can certainly cause the user program to crash by setting garbage but that's to be expected.
So i think dropping 2/3 in the list is good. If you concur i'll do that.