On Thu, 7 Dec 2000, Tigran Aivazian wrote:
> On Thu, 7 Dec 2000, Szabolcs Szakacsits wrote:
> > again. The failed logic is also clear from the kernel code [user
> > happily allocates when freelist < NR_RESERVED_FILES].
>
> is it clear to you? it is not clear to me, or rather the opposite seems
> clear. This is what the code looks like (in 2.4):
>
> struct file * get_empty_filp(void)
> {
> static int old_max = 0;
> struct file * f;
>
> file_list_lock();
> if (files_stat.nr_free_files > NR_RESERVED_FILES) {
> used_one:
> f = list_entry(free_list.next, struct file, f_list);
> list_del(&f->f_list);
> files_stat.nr_free_files--;
>
> so, a normal user is only allowed to allocate from the freelist when the
> number of elements on the freelist is > NR_RESERVED_FILES. I do not see
> how you are able to take elements from the freelist when the number is <
> NR_RESERVED_FILES unless you are a super-user, i.e. current->euid == 0.
Read the whole get_empty_filp function, especially this part, note the
goto new_one below and the part you didn't include above [from
the new_one label],
if (files_stat.nr_files < files_stat.max_files) {
file_list_unlock();
f = kmem_cache_alloc(filp_cachep, SLAB_KERNEL);
file_list_lock();
if (f) {
files_stat.nr_files++;
goto new_one;
}
> Btw, while you are there (in 2.2 kernel) you may want to fix the
Sorry, no time.
Szaka
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