linux-kernel - Re: [patch 1/2] timerfd add flags check

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Message-ID: <cfd18e0f0902081538p7021481eq5025e85a1f10642f@mail.gmail.com>
Date:	Mon, 9 Feb 2009 12:38:10 +1300
From:	Michael Kerrisk <mtk.manpages@...glemail.com>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch 1/2] timerfd add flags check

On Mon, Feb 9, 2009 at 12:23 PM, Davide Libenzi <davidel@...ilserver.org> wrote:
> Like Michael requested, this patch adds a missing check for valid flags in
> timerfd_settime(), and make it return EINVAL in case some extra bits are
> set. If this is or not a -stable thing, it Greg decision.
> Should be queued by Andrew for .30, unless -stable and Linus decide to
> get it before, like Michael suggested.

If this is to be any use to userland apps that want to check flag
support (perhaps it is too late already), then the sooner we get it
into the kernel the better: 2.6.29 would be good; earlier stables as
well would be even better.

Acked-by: Michael Kerrisk <mtk.manpages@...il.com>

> - Davide
>
>
> ---
>  fs/timerfd.c            |   12 ++++++------
>  include/linux/timerfd.h |   17 ++++++++++++++---
>  2 files changed, 20 insertions(+), 9 deletions(-)
>
> Index: linux-2.6.mod/fs/timerfd.c
> ===================================================================
> --- linux-2.6.mod.orig/fs/timerfd.c     2009-02-08 14:51:12.000000000 -0800
> +++ linux-2.6.mod/fs/timerfd.c  2009-02-08 14:55:32.000000000 -0800
> @@ -186,10 +186,9 @@ SYSCALL_DEFINE2(timerfd_create, int, clo
>        BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
>        BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
>
> -       if (flags & ~(TFD_CLOEXEC | TFD_NONBLOCK))
> -               return -EINVAL;
> -       if (clockid != CLOCK_MONOTONIC &&
> -           clockid != CLOCK_REALTIME)
> +       if ((flags & ~TFD_CREATE_FLAGS) ||
> +           (clockid != CLOCK_MONOTONIC &&
> +            clockid != CLOCK_REALTIME))
>                return -EINVAL;
>
>        ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> @@ -201,7 +200,7 @@ SYSCALL_DEFINE2(timerfd_create, int, clo
>        hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
>
>        ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
> -                              flags & (O_CLOEXEC | O_NONBLOCK));
> +                              flags & TFD_SHARED_FCNTL_FLAGS);
>        if (ufd < 0)
>                kfree(ctx);
>
> @@ -219,7 +218,8 @@ SYSCALL_DEFINE4(timerfd_settime, int, uf
>        if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
>                return -EFAULT;
>
> -       if (!timespec_valid(&ktmr.it_value) ||
> +       if ((flags & ~TFD_SETTIME_FLAGS) ||
> +           !timespec_valid(&ktmr.it_value) ||
>            !timespec_valid(&ktmr.it_interval))
>                return -EINVAL;
>
> Index: linux-2.6.mod/include/linux/timerfd.h
> ===================================================================
> --- linux-2.6.mod.orig/include/linux/timerfd.h  2009-02-08 14:51:12.000000000 -0800
> +++ linux-2.6.mod/include/linux/timerfd.h       2009-02-08 14:53:00.000000000 -0800
> @@ -11,13 +11,24 @@
>  /* For O_CLOEXEC and O_NONBLOCK */
>  #include <linux/fcntl.h>
>
> -/* Flags for timerfd_settime.  */
> +/*
> + * CAREFUL: Check include/asm-generic/fcntl.h when defining
> + * new flags, since they might collide with O_* ones. We want
> + * to re-use O_* flags that couldn't possibly have a meaning
> + * from eventfd, in order to leave a free define-space for
> + * shared O_* flags.
> + */
>  #define TFD_TIMER_ABSTIME (1 << 0)
> -
> -/* Flags for timerfd_create.  */
>  #define TFD_CLOEXEC O_CLOEXEC
>  #define TFD_NONBLOCK O_NONBLOCK
>
> +#define TFD_SHARED_FCNTL_FLAGS (TFD_CLOEXEC | TFD_NONBLOCK)
> +/* Flags for timerfd_create.  */
> +#define TFD_CREATE_FLAGS TFD_SHARED_FCNTL_FLAGS
> +/* Flags for timerfd_settime.  */
> +#define TFD_SETTIME_FLAGS TFD_TIMER_ABSTIME
> +#define TFD_FLAGS_SET (TFD_SHARED_FCNTL_FLAGS | TFD_TIMER_ABSTIME)
> +
>
>  #endif /* _LINUX_TIMERFD_H */
>
>



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
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