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SubjectRe: [patch] timerfd add flags check
From
On Tue, Feb 10, 2009 at 12:31 PM, Davide Libenzi
<davidel@xmailserver.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.
>
> Michael said:
> 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@gmail.com>
>
>
> Signed-off-by: Davide Libenzi <davidel@xmailserver.org>

Davide, one question: is the TFD_FLAGS_SET constant below needed?

cheers,

Michael

> ---
> 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 18:36:45.000000000 -0800
> +++ linux-2.6.mod/fs/timerfd.c 2009-02-08 18:53:32.000000000 -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 18:36:45.000000000 -0800
> +++ linux-2.6.mod/include/linux/timerfd.h 2009-02-08 18:41:22.000000000 -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
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html


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