linux-kernel - Re: [PATCH 12/20] fanotify: allow userspace to override max marks

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Message-ID: <201011011716.01875.tvrtko.ursulin@sophos.com>
Date:	Mon, 1 Nov 2010 17:16:01 +0000
From:	Tvrtko Ursulin <tvrtko.ursulin@...hos.com>
To:	Eric Paris <eparis@...hat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"agruen@...e.de" <agruen@...e.de>
Subject: Re: [PATCH 12/20] fanotify: allow userspace to override max marks

On Thursday 28 Oct 2010 22:32:44 Eric Paris wrote:
> Some fanotify groups, especially those like AV scanners, will need to place
> lots of marks, particularly ignore marks.  Since ignore marks do not pin
> inodes in cache and are cleared if the inode is removed from core (usually
> under memory pressure) we expose an interface for listeners, with
> CAP_SYS_ADMIN, to override the maximum number of marks and be allowed to
> set and 'unlimited' number of marks.  Programs which make use of this
> feature will be able to OOM a machine.
>
> Signed-off-by: Eric Paris <eparis@...hat.com>
> ---
>
>  fs/notify/fanotify/fanotify_user.c |    9 ++++++++-
>  include/linux/fanotify.h           |    4 +++-
>  2 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c
> b/fs/notify/fanotify/fanotify_user.c index 1d33d7d..f921610 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -707,7 +707,14 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags,
> unsigned int, event_f_flags) group->max_events =
> FANOTIFY_DEFAULT_MAX_EVENTS;
>       }
>
> -     group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
> +     if (flags & FAN_UNLIMITED_MARKS) {
> +             fd = -EPERM;
> +             if (!capable(CAP_SYS_ADMIN))
> +                     goto out_put_group;

Same redundant (or not) capable as with queue depth.

Tvrtko

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