[PATCH 5.9 355/391] futex: Adjust absolute futex timeouts with per time namespace offset

[Greg Kroah-Hartman]

From: Andrei Vagin <avagin@xxxxxxxxx>

commit c2f7d08cccf4af2ce6992feaabb9e68e4ae0bff3 upstream.

For all commands except FUTEX_WAIT, the 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.

Fixes: 5a590f35add9 ("posix-clocks: Wire up clock_gettime() with timens offsets")
Reported-by: Hans van der Laan <j.h.vanderlaan@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20201015160020.293748-1-avagin@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- 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>
 
@@ -3799,6 +3800,8 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad
 		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;
 	}
 	/*
@@ -3991,6 +3994,8 @@ SYSCALL_DEFINE6(futex_time32, u32 __user
 		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 ||