[PATCH] epoll: Check for fdtable races

[PATCH] epoll: Check for fdtable races

[Matt Helsley]

In case it's possible to race with other tasks sharing the fdtable,
check for NULL file * and exit with an error.

Please consider merging this with the first patch in the series
of epoll patches posted recently.

Reported-by: "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Matt Helsley <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Cc: "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 fs/eventpoll.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index c261263..638f9d7 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1677,7 +1677,8 @@ struct file* ep_file_restore(struct ckpt_ctx *ctx,
 		return ERR_PTR(epfd);
 	epfile = fget(epfd);
 	sys_close(epfd); /* harmless even if an error occured */
-	BUG_ON(!epfile);
+	if (!epfile)
+		return ERR_PTR(-EBADF);
 
 	/*
 	 * Needed before we can properly restore the watches and enforce the
-- 
1.5.6.3

Re: [PATCH] epoll: Check for fdtable races

[Oren Laadan]

Matt Helsley wrote:
> In case it's possible to race with other tasks sharing the fdtable,
> check for NULL file * and exit with an error.
> 
> Please consider merging this with the first patch in the series
> of epoll patches posted recently.
> 
> Reported-by: "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Matt Helsley <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> Cc: "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

Already did that when I pulled your patch.

BTW, I chose -EBUSY instead to tell the user to try again
later... when he/she isn't malicious anymore :)

Oren.

> ---
>  fs/eventpoll.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index c261263..638f9d7 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -1677,7 +1677,8 @@ struct file* ep_file_restore(struct ckpt_ctx *ctx,
>  		return ERR_PTR(epfd);
>  	epfile = fget(epfd);
>  	sys_close(epfd); /* harmless even if an error occured */
> -	BUG_ON(!epfile);
> +	if (!epfile)
> +		return ERR_PTR(-EBADF);
>  
>  	/*
>  	 * Needed before we can properly restore the watches and enforce the

Re: [PATCH] epoll: Check for fdtable races

[Serge E. Hallyn]

Quoting Oren Laadan (orenl-RdfvBDnrOixBDgjK7y7TUQ@public.gmane.org):
> 
> 
> Matt Helsley wrote:
> > In case it's possible to race with other tasks sharing the fdtable,
> > check for NULL file * and exit with an error.
> > 
> > Please consider merging this with the first patch in the series
> > of epoll patches posted recently.
> > 
> > Reported-by: "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> > Signed-off-by: Matt Helsley <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> > Cc: "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> 
> Already did that when I pulled your patch.
> 
> BTW, I chose -EBUSY instead to tell the user to try again
> later... when he/she isn't malicious anymore :)

"Go stand in the corner and don't come out until you'll
be NICE to your brother!"

-serge