On Tue, Feb 27, 2018 at 2:43 PM, Danilo Krummrich
<danilokrummrich@xxxxxxxxxxxxx> wrote:
> proc_sys_link_fill_cache() does not take currently unregistering
> sysctl tables into account, which might result into a page fault in
> sysctl_follow_link() - add a check to fix it.
>
> Signed-off-by: Danilo Krummrich <danilokrummrich@xxxxxxxxxxxxx>
> ---
> fs/proc/proc_sysctl.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c5cbbdff3c3d..a0b6c647835e 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -709,6 +709,9 @@ static bool proc_sys_link_fill_cache(struct file *file,
> bool ret = true;
Nothing appears to actually change "ret" in this function. It should
likely be dropped too.
> head = sysctl_head_grab(head);
>
> + if (IS_ERR(head))
> + return false;
> +
This looks sensible. I'd drop the blank line between sysctl_head_grab
and the IS_ERR, though.
How are you testing this change?
Thanks!
-Kees
> if (S_ISLNK(table->mode)) {
> /* It is not an error if we can not follow the link ignore it */
> int err = sysctl_follow_link(&head, &table);
> --
> 2.14.1
>
--
Kees Cook
Pixel Security
