On Tue 20-08-13 11:23:24, Chen Gang wrote:
> '*lenp' may be less than "sizeof(kbuf)", need check it before the next
> copy_to_user().
>
> pdflush_proc_obsolete() is called by sysctl which 'procname' is
> "nr_pdflush_threads", if the user passes buffer length less than
> "sizeof(kbuf)", it will cause issue.
>
Good catch. The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
>
> Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
> ---
> mm/backing-dev.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index e04454c..2674671 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -649,7 +649,7 @@ int pdflush_proc_obsolete(struct ctl_table *table, int write,
> {
> char kbuf[] = "0\n";
>
> - if (*ppos) {
> + if (*ppos || *lenp < sizeof(kbuf)) {
> *lenp = 0;
> return 0;
> }
> --
> 1.7.7.6
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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