lkml.org 
[lkml]   [2000]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Broken NR_RESERVED_FILES

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

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:51    [W:0.029 / U:8.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site