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SubjectRe: [PATCH v2 1/2] fs/sysctl: fix potential page fault while unregistering sysctl table
On Wed, Feb 28, 2018 at 12:31:55AM +0100, Danilo Krummrich 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@dk-develop.de>
> ---
> v2: removed empty line between between sysctl_head_grab and IS_ERR

Please add a respective tag:

Fixes: 0e47c99d7fe25 ("sysctl: Replace root_list with links between sysctl_table_sets")

And mention this has been present since v3.4. May be worth sending to
stable as well, so peg stable as well.

Luis

> ---
> 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..82ac5f682b73 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -707,7 +707,10 @@ static bool proc_sys_link_fill_cache(struct file *file,
> struct ctl_table *table)
> {
> bool ret = true;
> +
> head = sysctl_head_grab(head);
> + if (IS_ERR(head))
> + return false;
>
> if (S_ISLNK(table->mode)) {
> /* It is not an error if we can not follow the link ignore it */
> --
> 2.14.1
>
>

--
Luis Rodriguez, SUSE LINUX GmbH
Maxfeldstrasse 5; D-90409 Nuernberg

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