[tip: timers/urgent] futex: Adjust futex absolute timeouts with per-timens offset

["tip-bot2 for Andrei Vagin" <tip-bot2@linutronix.de>]

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     06764291690f8650a9f96dea42cc0dd4138d47d5
Gitweb:        https://git.kernel.org/tip/06764291690f8650a9f96dea42cc0dd4138d47d5
Author:        Andrei Vagin <avagin@gmail.com>
AuthorDate:    Thu, 15 Oct 2020 00:29:08 -07:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 15 Oct 2020 11:24:04 +02:00

futex: Adjust futex absolute timeouts with per-timens offset

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.

Fixes: 5a590f35add9 ("posix-clocks: Wire up clock_gettime() with timens offsets")
Reported-by: Hans van der Laan <j.h.vanderlaan@student.utwente.nl>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201015072909.271426-1-avagin@gmail.com

---
 kernel/futex.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/futex.c b/kernel/futex.c
index a587669..9ff2b8c 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 (!(cmd & FUTEX_CLOCK_REALTIME))
+			t = timens_ktime_to_host(CLOCK_MONOTONIC, t);
 		tp = &t;
 	}
 	/*