Sorry for delay...
On 10/13, Tycho Andersen wrote:
>
> --- a/include/uapi/linux/ptrace.h
> +++ b/include/uapi/linux/ptrace.h
> @@ -23,6 +23,8 @@
>
> #define PTRACE_SYSCALL 24
>
> +#define PTRACE_SECCOMP_GET_FILTER 40
Probably it would be better to add this at the end of other 0x42..
constants? After PTRACE_SETSIGMASK.
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -347,6 +347,7 @@ static struct seccomp_filter
> *seccomp_prepare_filter(struct sock_fprog *fprog)
> {
> struct seccomp_filter *sfilter;
> int ret;
> + const bool save_orig = config_enabled(CONFIG_CHECKPOINT_RESTORE);
>
> if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
> return ERR_PTR(-EINVAL);
> @@ -370,7 +371,7 @@ static struct seccomp_filter
> *seccomp_prepare_filter(struct sock_fprog *fprog)
> return ERR_PTR(-ENOMEM);
>
> ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
> - seccomp_check_filter, false);
> + seccomp_check_filter, save_orig);
Can't comment, this depends on other changes I missed... but I don't
this you need my review here ;)
> +#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
> +long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
> + void __user *data)
> +{
> + struct seccomp_filter *filter;
> + struct sock_fprog_kern *fprog;
> + long ret;
> + unsigned long count = 0;
> +
> + spin_lock_irq(¤t->sighand->siglock);
> + if (!capable(CAP_SYS_ADMIN) ||
> + current->seccomp.mode != SECCOMP_MODE_DISABLED) {
> + ret = -EACCES;
> + goto out_self;
> + }
> +
> + spin_lock_irq(&task->sighand->siglock);
Oh, no, you can't do this.
This is deadlockable. Suppose that this task's sub-thread traces the
caller (the current task) and does PTRACE_SECCOMP_GET_FILTER too.
In this case it can take the same 2 locks in reverse order, deadlock.
But why do you need to hold both ->siglock's at the same time?
Oleg.
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