Re: io_uring: should IORING_TIMEOUT_ABS honour the submitter's time namespace?

[Pavel Begunkov <asml.silence@gmail.com>]

On 5/2/26 10:21, Xie Maoyi wrote:
> Hi all,
> 
> I think I have found what might be a bug in io_uring's absolute-deadline path on v7.0 mainline, and I would appreciate your confirmation on whether it is actually a bug and whether it is worth fixing.

timerfd seems to adjust it with timens_ktime_to_host(), maybe something
like below should do it, _not_ tested. FWIW, IORING_TIMEOUT_ABS is
much older than 7.0.


diff --git a/io_uring/timeout.c b/io_uring/timeout.c
index 4cfdfc519770..184d81a1d594 100644
--- a/io_uring/timeout.c
+++ b/io_uring/timeout.c
@@ -3,6 +3,7 @@
  #include <linux/errno.h>
  #include <linux/file.h>
  #include <linux/io_uring.h>
+#include <linux/time_namespace.h>
  
  #include <trace/events/io_uring.h>
  
@@ -35,6 +36,27 @@ struct io_timeout_rem {
  	bool				ltimeout;
  };
  
+static clockid_t io_flags_to_clock(unsigned flags)
+{
+	switch (flags & IORING_TIMEOUT_CLOCK_MASK) {
+	case IORING_TIMEOUT_BOOTTIME:
+		return CLOCK_BOOTTIME;
+	case IORING_TIMEOUT_REALTIME:
+		return CLOCK_REALTIME;
+	default:
+		/* can't happen, vetted at prep time */
+		WARN_ON_ONCE(1);
+		fallthrough;
+	case 0:
+		return CLOCK_MONOTONIC;
+	}
+}
+
+static clockid_t io_timeout_get_clock(struct io_timeout_data *data)
+{
+	return io_flags_to_clock(data->flags);
+}
+
  static int io_parse_user_time(ktime_t *time, u64 arg, unsigned flags)
  {
  	struct timespec64 ts;
@@ -43,7 +65,7 @@ static int io_parse_user_time(ktime_t *time, u64 arg, unsigned flags)
  		*time = ns_to_ktime(arg);
  		if (*time < 0)
  			return -EINVAL;
-		return 0;
+		goto out;
  	}
  
  	if (get_timespec64(&ts, u64_to_user_ptr(arg)))
@@ -51,6 +73,9 @@ static int io_parse_user_time(ktime_t *time, u64 arg, unsigned flags)
  	if (ts.tv_sec < 0 || ts.tv_nsec < 0)
  		return -EINVAL;
  	*time = timespec64_to_ktime(ts);
+out:
+	if (flags & IORING_TIMEOUT_ABS)
+		*time = timens_ktime_to_host(io_flags_to_clock(flags), *time);
  	return 0;
  }
  
@@ -397,22 +422,6 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
  	return HRTIMER_NORESTART;
  }
  
-static clockid_t io_timeout_get_clock(struct io_timeout_data *data)
-{
-	switch (data->flags & IORING_TIMEOUT_CLOCK_MASK) {
-	case IORING_TIMEOUT_BOOTTIME:
-		return CLOCK_BOOTTIME;
-	case IORING_TIMEOUT_REALTIME:
-		return CLOCK_REALTIME;
-	default:
-		/* can't happen, vetted at prep time */
-		WARN_ON_ONCE(1);
-		fallthrough;
-	case 0:
-		return CLOCK_MONOTONIC;
-	}
-}
-
  static int io_linked_timeout_update(struct io_ring_ctx *ctx, __u64 user_data,
  				    ktime_t ts, enum hrtimer_mode mode)
  	__must_hold(&ctx->timeout_lock)

-- 
Pavel Begunkov