On 09/20, Tycho Andersen wrote: > > Thanks for cleaning this up, I'll be happy to test whatever final > patch we come up with.
Well, I just noticed you sent another "[PATCH] ptrace, seccomp: add support for retrieving seccomp flags" today... So if we need get_nth() helper please consider the UNTESTED change below (on top of this fix). If you agree with this code, feel free to incorporate it into your patch. Oleg. --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -855,49 +855,54 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) } #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) -long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, - void __user *data) +static struct seccomp_filter * +get_nth_filter(struct task_struct *task, unsigned long filter_off) { - struct seccomp_filter *filter; - struct sock_fprog_kern *fprog; - long ret; - unsigned long count = 0; + struct seccomp_filter *orig, *filter; + unsigned long count; - if (!capable(CAP_SYS_ADMIN) || - current->seccomp.mode != SECCOMP_MODE_DISABLED) { - return -EACCES; - } + if (task->seccomp.mode != SECCOMP_MODE_FILTER) + return ERR_PTR(-EINVAL); spin_lock_irq(&task->sighand->siglock); - if (task->seccomp.mode != SECCOMP_MODE_FILTER) { - ret = -EINVAL; - goto out; - } + get_seccomp_filter(task); + orig = task->seccomp.filter; + spin_unlock_irq(&task->sighand->siglock); - filter = task->seccomp.filter; - while (filter) { - filter = filter->prev; + count = 0; + for (filter = orig; filter; filter = filter->prev) count++; - } - if (filter_off >= count) { - ret = -ENOENT; + filter = ERR_PTR(-ENOENT); + if (filter_off >= count) goto out; - } - count -= filter_off; - filter = task->seccomp.filter; - while (filter && count > 1) { - filter = filter->prev; + count -= filter_off; + for (filter = orig; count > 1; filter = filter->prev) count--; - } - if (WARN_ON(count != 1 || !filter)) { - /* The filter tree shouldn't shrink while we're using it. */ - ret = -ENOENT; - goto out; + refcount_inc(&filter->usage); +out: + __put_seccomp_filter(orig); + return filter; +} + +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; + + if (!capable(CAP_SYS_ADMIN) || + current->seccomp.mode != SECCOMP_MODE_DISABLED) { + return -EACCES; } + filter = get_nth_filter(task, filter_off); + if (IS_ERR(filter)) + return PTR_ERR(filter); + fprog = filter->prog->orig_prog; if (!fprog) { /* This must be a new non-cBPF filter, since we save @@ -912,17 +917,10 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, if (!data) goto out; - refcount_inc(&filter->usage); - spin_unlock_irq(&task->sighand->siglock); - if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) ret = -EFAULT; - - __put_seccomp_filter(filter); - return ret; - out: - spin_unlock_irq(&task->sighand->siglock); + __put_seccomp_filter(filter); return ret; } #endif