[Acked] [PATCH Trusty SRU] fanotify: fix -EOVERFLOW with large files on 64-bit

[Andy Whitcroft]

On Fri, Dec 18, 2015 at 05:59:49AM -0700, tim.gardner at canonical.com wrote:
> From: Will Woods <wwoods at redhat.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1527039
> 
> On 64-bit systems, O_LARGEFILE is automatically added to flags inside
> the open() syscall (also openat(), blkdev_open(), etc).  Userspace
> therefore defines O_LARGEFILE to be 0 - you can use it, but it's a
> no-op.  Everything should be O_LARGEFILE by default.
> 
> But: when fanotify does create_fd() it uses dentry_open(), which skips
> all that.  And userspace can't set O_LARGEFILE in fanotify_init()
> because it's defined to 0.  So if fanotify gets an event regarding a
> large file, the read() will just fail with -EOVERFLOW.
> 
> This patch adds O_LARGEFILE to fanotify_init()'s event_f_flags on 64-bit
> systems, using the same test as open()/openat()/etc.
> 
> Addresses https://bugzilla.redhat.com/show_bug.cgi?id=696821
> 
> Signed-off-by: Will Woods <wwoods at redhat.com>
> Acked-by: Eric Paris <eparis at redhat.com>
> Reviewed-by: Jan Kara <jack at suse.cz>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> (back ported from commit 1e2ee49f7f1b79f0b14884fe6a602f0411b39552)
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
> ---
>  fs/notify/fanotify/fanotify_user.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index cc80b0a..864bd62 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -727,6 +727,8 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
>  	group->fanotify_data.user = user;
>  	atomic_inc(&user->fanotify_listeners);
>  
> +	if (force_o_largefile())
> +		event_f_flags |= O_LARGEFILE;
>  	group->fanotify_data.f_flags = event_f_flags;
>  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
>  	mutex_init(&group->fanotify_data.access_mutex);


Looks to do what is claimed.

Acked-by: Andy Whitcroft <apw at canonical.com>

-apw