[PATCH 1/2 v2] futex: adjust a futex timeout with a per-timens offset

[Andrei Vagin]

For all commands except FUTEX_WAIT, timeout is interpreted as an
absolute value. This absolute value is inside the task's time namespace
and has to be converted to the host's time.

Cc: <sta...@vger.kernel.org>
Fixes: 5a590f35add9 ("posix-clocks: Wire up clock_gettime() with timens 
offsets")
Reported-by: Hans van der Laan <j.h.vanderl...@student.utwente.nl>
Signed-off-by: Andrei Vagin <ava...@gmail.com>
---

v2:
* check FUTEX_CLOCK_REALTIME properly
* fix futex_time32 too

 kernel/futex.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/futex.c b/kernel/futex.c
index a5876694a60e..32056d2d4171 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -39,6 +39,7 @@
 #include <linux/freezer.h>
 #include <linux/memblock.h>
 #include <linux/fault-inject.h>
+#include <linux/time_namespace.h>
 
 #include <asm/futex.h>
 
@@ -3797,6 +3798,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, 
val,
                t = timespec64_to_ktime(ts);
                if (cmd == FUTEX_WAIT)
                        t = ktime_add_safe(ktime_get(), t);
+               else if (!(op & FUTEX_CLOCK_REALTIME))
+                       t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
                tp = &t;
        }
        /*
@@ -3989,6 +3992,8 @@ SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, 
op, u32, val,
                t = timespec64_to_ktime(ts);
                if (cmd == FUTEX_WAIT)
                        t = ktime_add_safe(ktime_get(), t);
+               else if (!(op & FUTEX_CLOCK_REALTIME))
+                       t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
                tp = &t;
        }
        if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
-- 
2.26.2