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[PATCH 2/2] io_getevents: Use timespec64 to represent timeouts

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  [PATCH 2/2] io_getevents: Use timespec64 to represent timeouts Deepa Dinamani <deepa.kernel@gmail.com> - 2017-08-05 06:20 +0200
    Re: [PATCH 2/2] io_getevents: Use timespec64 to represent timeouts Arnd Bergmann <arnd@arndb.de> - 2017-08-05 22:20 +0200
      Re: [PATCH 2/2] io_getevents: Use timespec64 to represent timeouts Deepa Dinamani <deepa.kernel@gmail.com> - 2017-08-06 05:50 +0200

#1704561 — [PATCH 2/2] io_getevents: Use timespec64 to represent timeouts

struct timespec is not y2038 safe. Use y2038 safe
struct timespec64 to represent timeouts.
The system call interface itself will be changed as
part of different series.

Timeouts will not really need more than 32 bits.
But, replacing these with timespec64 helps verification
of a y2038 safe kernel by getting rid of timespec
internally.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: linux-aio@kvack.org
---
 fs/aio.c | 55 ++++++++++++++++++++++++++++++-------------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 8f0127526299..7ca6b7a00368 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1289,20 +1289,10 @@ static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
 
 static long read_events(struct kioctx *ctx, long min_nr, long nr,
 			struct io_event __user *event,
-			struct timespec __user *timeout)
+			ktime_t until)
 {
-	ktime_t until = KTIME_MAX;
 	long ret = 0;
 
-	if (timeout) {
-		struct timespec	ts;
-
-		if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
-			return -EFAULT;
-
-		until = timespec_to_ktime(ts);
-	}
-
 	/*
 	 * Note that aio_read_events() is being called as the conditional - i.e.
 	 * we're calling it after prepare_to_wait() has set task state to
@@ -1824,6 +1814,25 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
 	return ret;
 }
 
+static long do_io_getevents(aio_context_t ctx_id,
+		long min_nr,
+		long nr,
+		struct io_event __user *events,
+		struct timespec64 *ts)
+{
+	ktime_t until = ts ? timespec64_to_ktime(*ts) : KTIME_MAX;
+	struct kioctx *ioctx = lookup_ioctx(ctx_id);
+	long ret = -EINVAL;
+
+	if (likely(ioctx)) {
+		if (likely(min_nr <= nr && min_nr >= 0))
+			ret = read_events(ioctx, min_nr, nr, events, until);
+		percpu_ref_put(&ioctx->users);
+	}
+
+	return ret;
+}
+
 /* io_getevents:
  *	Attempts to read at least min_nr events and up to nr events from
  *	the completion queue for the aio_context specified by ctx_id. If
@@ -1842,15 +1851,14 @@ SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
 		struct io_event __user *, events,
 		struct timespec __user *, timeout)
 {
-	struct kioctx *ioctx = lookup_ioctx(ctx_id);
-	long ret = -EINVAL;
+	struct timespec64	ts;
 
-	if (likely(ioctx)) {
-		if (likely(min_nr <= nr && min_nr >= 0))
-			ret = read_events(ioctx, min_nr, nr, events, timeout);
-		percpu_ref_put(&ioctx->users);
+	if (timeout) {
+		if (unlikely(get_timespec64(&ts, timeout)))
+			return -EFAULT;
 	}
-	return ret;
+
+	return do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
 }
 
 #ifdef CONFIG_COMPAT
@@ -1860,17 +1868,14 @@ COMPAT_SYSCALL_DEFINE5(io_getevents, compat_aio_context_t, ctx_id,
 		       struct io_event __user *, events,
 		       struct compat_timespec __user *, timeout)
 {
-	struct timespec t;
-	struct timespec __user *ut = NULL;
+	struct timespec64 t;
 
 	if (timeout) {
-		if (compat_get_timespec(&t, timeout))
+		if (compat_get_timespec64(&t, timeout))
 			return -EFAULT;
 
-		ut = compat_alloc_user_space(sizeof(*ut));
-		if (copy_to_user(ut, &t, sizeof(t)))
-			return -EFAULT;
 	}
-	return sys_io_getevents(ctx_id, min_nr, nr, events, ut);
+
+	return do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
 }
 #endif
-- 
2.11.0

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#1704702

On Sat, Aug 5, 2017 at 6:12 AM, Deepa Dinamani <deepa.kernel@gmail.com> wrote:
> struct timespec is not y2038 safe. Use y2038 safe
> struct timespec64 to represent timeouts.
> The system call interface itself will be changed as
> part of different series.
>
> Timeouts will not really need more than 32 bits.
> But, replacing these with timespec64 helps verification
> of a y2038 safe kernel by getting rid of timespec
> internally.
>
> Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
> Cc: linux-aio@kvack.org

Nice cleanup of the compat path!

>  static long read_events(struct kioctx *ctx, long min_nr, long nr,
>                         struct io_event __user *event,
> -                       struct timespec __user *timeout)
> +                       ktime_t until)
>  {
> -       ktime_t until = KTIME_MAX;
>         long ret = 0;
>
> -       if (timeout) {
> -               struct timespec ts;
> -
> -               if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
> -                       return -EFAULT;
> -
> -               until = timespec_to_ktime(ts);
> -       }
> -
>         /*
>          * Note that aio_read_events() is being called as the conditional - i.e.
>          * we're calling it after prepare_to_wait() has set task state to
> @@ -1824,6 +1814,25 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
>         return ret;
>  }
>
> +static long do_io_getevents(aio_context_t ctx_id,
> +               long min_nr,
> +               long nr,
> +               struct io_event __user *events,
> +               struct timespec64 *ts)
> +{
> +       ktime_t until = ts ? timespec64_to_ktime(*ts) : KTIME_MAX;
> +       struct kioctx *ioctx = lookup_ioctx(ctx_id);
> +       long ret = -EINVAL;
> +
> +       if (likely(ioctx)) {
> +               if (likely(min_nr <= nr && min_nr >= 0))
> +                       ret = read_events(ioctx, min_nr, nr, events, until);
> +               percpu_ref_put(&ioctx->users);
> +       }
> +
> +       return ret;
> +}

I guess these two functions are small enough that they could be merged
into one, saving a few lines. Then again, fs/aio.c seems to generally use
fairly short functions doing not too much at once, so your approach maybe
fits better with the style of the subsystem.

Either way,

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

       Arnd

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#1704740

> I guess these two functions are small enough that they could be merged
> into one, saving a few lines. Then again, fs/aio.c seems to generally use
> fairly short functions doing not too much at once, so your approach maybe
> fits better with the style of the subsystem.

I don't see a problem with combining the two functions either.
Unless someone has a strong preference, I will leave it the way it is
currently handled.

Thanks,
Deepa

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